Atmos Energy (ATO) 424B5 Prospectus supplement for primary offering

Filed Pursuant to Rule 424(b)(5)

RegistrationNo. 333-236369

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities to be Registered	Proposed Maximum Aggregate Offering Price	Amount of Registration Fee(1)
Common stock, no par value per share	$1,000,000,000	$129,800

(1) Calculated in accordance with Rule 457(o) under the Securities Act, based on the Proposed Maximum Aggregate Offering Price.

Prospectus supplement

(To prospectus dated February 11, 2020)

Atmos Energy Corporation

Common stock

Having an Aggregate Offering Price of up to $1,000,000,000

This prospectus supplement and the accompanying base prospectus relate to the offer and sale from time to time of shares of common stock of Atmos Energy Corporation having an aggregate offering price of up to $1,000,000,000 through one or more of the sales agents named in this prospectus supplement (the “sales agents”). These sales will be made over a period of time and from time to time in transactions at then-current prices, pursuant to an equity distribution agreement between us and the sales agents. The equity distribution agreement provides that, in addition to the issuance and sale of common stock by us through the sales agents, we also may enter into forward sale agreements under separate master forward sale confirmations and related supplemental confirmations between us and each of Morgan Stanley & Co. LLC, BNP Paribas, Canadian Imperial Bank of Commerce, Credit Agricole Corporate and Investment Bank c/o Credit Agricole Securities (USA) Inc., as Agent, Goldman Sachs & Co. LLC, JPMorgan Chase Bank, National Association, Bank of America N.A., Mizuho Securities USA LLC, MUFG Securities EMEA plc, The Toronto-Dominion Bank and Wells Fargo Bank, National Association. We refer to these entities, when acting in such capacity, as forward purchasers. In connection with each forward sale agreement, the relevant forward purchaser will, at our request, borrow from third parties and, through the relevant sales agent, sell a number of shares of our common stock equal to the number of shares of our common stock that underlie the forward sale agreement to hedge the forward sale agreement. We refer to each of Morgan Stanley & Co. LLC, BofA Securities, Inc., BNP Paribas Securities Corp., CIBC World Markets Corp., Credit Agricole Securities (USA) Inc., Goldman Sachs & Co. LLC, J.P. Morgan Securities LLC, Mizuho Securities USA LLC, MUFG Securities Americas Inc., SunTrust Robinson Humphrey, Inc., TD Securities (USA) LLC and Wells Fargo Securities, LLC, when acting as the agent for a forward purchaser, as a forward seller. In no event will the aggregate number of shares of our common stock sold through the sales agents as our agents and by the forward sellers under the equity distribution agreement have an aggregate sales price in excess of $1,000,000,000.

We will not initially receive any proceeds from the sale of borrowed shares of our common stock by a forward seller. We expect to receive proceeds from the sale of shares of our common stock upon future physical settlement of the relevant forward sale agreement with the relevant forward purchaser on dates specified by us on or prior to the maturity date of the relevant forward sale agreement. If we elect to cash settle or net share settle a forward sale agreement, we may not (in the case of cash settlement) or will not (in the case of net share settlement) receive any proceeds, and we may owe cash (in the case of cash settlement) or shares of our common stock (in the case of net share settlement) to the relevant forward purchaser.

Sales of common stock under this prospectus supplement, if any, will be made by means of ordinary brokers’ transactions through the facilities of the New York Stock Exchange (the “NYSE”), at market prices, in block transactions or as otherwise agreed between us and the sales agents. The sales agents are not required to sell any specific dollar amount of shares of common stock but will use their commercially reasonable efforts, as our agents and subject to the terms of the equity distribution agreement, to sell the shares offered as instructed by us.

The compensation to the sales agents for sales of common stock will be a fixed commission rate of 1.00% of the gross sales price per share. See “Plan of Distribution (Conflicts of Interest)” beginning on pageS-16 for additional information regarding the compensation to be paid to the sales agents. In connection with each forward sale agreement, the relevant forward seller will receive, reflected in a reduced initial forward sale price payable by the relevant forward purchaser under its forward sale agreement, a commission of 1.00% of the volume weighted average of the sales prices of all borrowed shares of our common stock sold during the applicable period by it as a forward seller. The net proceeds from any sales under this prospectus supplement will be used as described under “Use of Proceeds.”

Our common stock is listed on the NYSE under the symbol “ATO.” The last reported sales price of our common stock on February 11, 2020 was $119.35.

Investing in our common stock involves risks. See “Risk Factors” beginning on pageS-3 of this prospectus supplement and page 3 of the accompanying prospectus.

Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement. Any representation to the contrary is a criminal offense.

Morgan Stanley	BofA Securities	BNP PARIBAS	CIBC Capital Markets
Credit Agricole CIB	Goldman Sachs & Co. LLC	J.P. Morgan	Mizuho Securities
MUFG	SunTrust Robinson Humphrey	TD Securities	Wells Fargo Securities

The date of this prospectus supplement is February 12, 2020.

TABLE OF CONTENTS

Prospectus Supplement

	Page
Important Notice About Information in this Prospectus Supplement and the Accompanying Prospectus		S-i
Cautionary Statement Regarding Forward-Looking Statements		S-ii
Prospectus Supplement Summary		S-1
Risk Factors		S-3
Use of Proceeds		S-7
Business		S-8
Certain U.S. Federal Income Tax Considerations forNon-U.S. Holders		S-12
Plan of Distribution (Conflicts of Interest)		S-16
Legal Matters		S-21
Experts		S-21
Incorporation of Certain Documents by Reference		S-22

Prospectus

	Page
Cautionary Statement Regarding Forward-Looking Statements		1
Risk Factors		3
Atmos Energy Corporation		3
Securities We May Offer		3
Use of Proceeds		4
Description of Debt Securities		4
Description of Common Stock		20
Plan of Distribution		22
Legal Matters		24
Experts		24
Where You Can Find More Information		24
Incorporation of Certain Documents by Reference		25

IMPORTANT NOTICE ABOUT INFORMATION IN THIS

PROSPECTUS SUPPLEMENT AND THE ACCOMPANYING PROSPECTUS

This document consists of two parts. The first part is this prospectus supplement, which describes the specific terms of this offering of our common stock and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus. The second part is the accompanying prospectus, dated February 11, 2020, which gives more general information, some of which does not apply to this offering. To the extent there is a conflict between the information contained in this prospectus supplement, the information contained in the accompanying prospectus or the information contained in any document incorporated by reference herein or therein, the information contained in the most recent document shall control. This prospectus supplement and the accompanying prospectus are a part of a registration statement that we filed with the SEC using the SEC’s shelf registration rules.

We have not, and the sales agents, forward sellers and forward purchasers have not, authorized any other person to provide you with information other than information provided or incorporated by reference in this prospectus supplement, the accompanying prospectus or any free writing prospectus relating to the offerings of common stock made pursuant to this prospectus supplement. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you or representations that others may make. See “Incorporation of Certain Documents by Reference” and “Where You Can Find More Information” in the accompanying prospectus.

Neither Atmos Energy Corporation nor the sales agents, forward sellers or forward purchasers are making an offer of this common stock in any jurisdiction where the offer is not permitted.

The information contained in or incorporated by reference in this document is accurate only as of the date of this prospectus supplement or the date of such incorporated documents, regardless of the time of delivery of this prospectus supplement or of any sale of common stock. Our business, financial condition, results of operations and prospects may have changed since those respective dates.

The terms “we,” “our,” “us,” and “Atmos Energy” refer to Atmos Energy Corporation and its subsidiaries unless the context suggests otherwise. The term the “Company” refers to Atmos Energy Corporation and not its subsidiaries. The term “you” refers to a prospective investor.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Statements contained or incorporated by reference in this prospectus supplement and the accompanying prospectus that are not statements of historical fact are “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”) and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Forward-looking statements are based on management’s beliefs as well as assumptions made by, and information currently available to, management. Because such statements are based on expectations as to future results and are not statements of fact, actual results may differ materially from those stated. Important factors that could cause future results to differ include, but are not limited to:

• state and local regulatory trends and decisions, including the impact of rate proceedings before various state regulatory commissions;

• increased federal regulatory oversight and potential penalties;

• possible increased federal, state and local regulation of the safety of our operations;

• possible significant costs and liabilities resulting from pipeline integrity and other similar programs and related repairs;

• the inherent hazards and risks involved in distributing, transporting and storing natural gas;

• the capital-intensive nature of our business;

• our ability to continue to access the credit and capital markets to execute our business strategy;

• market risks beyond our control affecting our risk management activities, including commodity price volatility, counterparty performance or creditworthiness and interest rate risk;

• the concentration of our operations in Texas;

• the impact of adverse economic conditions on our customers;

• changes in the availability and price of natural gas;

• the availability and accessibility of contracted gas supplies, interstate pipeline and/or storage services;

• increased competition from energy suppliers and alternative forms of energy;

• adverse weather conditions;

• increased costs of providing health care benefits, along with pension and postretirement health care benefits and increased funding requirements;

• the inability to continue to hire, train and retain operational, technical and managerial personnel;

• the impact of climate change;

• the impact of greenhouse gas emissions or other legislation or regulations intended to address climate change;

• increased dependence on technology that may hinder the Company’s business if such technologies fail;

• the threat of cyber-attacks or acts of cyber-terrorism that could disrupt our business operations and information technology systems or result in the loss or exposure of confidential or sensitive customer, employee or Company information;

• natural disasters, terrorist activities or other events; and

• other risks and uncertainties discussed in this prospectus, any accompanying prospectus supplement and our other filings with the Securities and Exchange Commission (the “SEC”).

All of these factors are difficult to predict and many are beyond our control. Accordingly, while we believe these forward-looking statements to be reasonable, there can be no assurance that they will approximate actual

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experience or that the expectations derived from them will be realized. When used in our documents or oral presentations, the words “anticipate,” “believe,” “estimate,” “expect,” forecast,” “goal,” “intend,” “objective,” “plan,” “projection,” “seek,” “strategy” or similar words are intended to identify forward-looking statements. We undertake no obligation to update or revise any of our forward-looking statements, whether as a result of new information, future events or otherwise.

For additional factors you should consider, please see “Risk Factors” on pageS-3 of this prospectus supplement, “Item 1A. Risk Factors” and “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our Annual Report on Form10-K for the fiscal year ended September 30, 2019. See also “Incorporation of Certain Documents by Reference” in the accompanying prospectus.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary does not contain all of the information that you should consider before investing in our common stock. You should read the following summary in conjunction with the more detailed information contained elsewhere in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus.

Atmos Energy Corporation

Atmos Energy Corporation, headquartered in Dallas, Texas, and incorporated in Texas and Virginia, is one of the country’s largestnatural-gas-only distributors based on number of customers. We deliver natural gas through regulated sales and transportation arrangements to over three million residential, commercial, public authority and industrial customers in eight states located primarily in the South. We also operate one of the largest intrastate pipelines in Texas based on miles of pipe.

We manage and review our consolidated operations through the following reportable segments:

• Thedistribution segment is primarily comprised of our regulated natural gas distribution and related sales operations in eight states.

• Thepipeline and storage segment is comprised primarily of the pipeline and storage operations of our Atmos Pipeline—Texas Division and our natural gas transmission operations in Louisiana.

Recent Developments

Declaration of Dividend. On February 4, 2020, our Board of Directors declared a dividend of $0.575 per share payable on March 9, 2020 to shareholders of record on February 24, 2020.

Our address is 1800 Three Lincoln Centre, 5430 LBJ Freeway, Dallas, Texas 75240, and our telephone number is(972) 934-9227. Our website iswww.atmosenergy.com; any information on or connected to our website is not part of this prospectus supplement or the accompanying prospectus.

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The Offering

Common stock offered by us Shares of common stock having an aggregate offering price of up to $1,000,000,000.

Use of proceeds We intend to use the net proceeds we receive upon the issuance and sale of shares of our common stock to repay short-term debt under our commercial paper program, to fund capital spending primarily to enhance the safety and reliability of our system and for general corporate purposes.

We will not initially receive any proceeds from the sale of borrowed shares of our common stock by the forward sellers in connection with any forward sale agreement as a hedge of the forward sale agreement. We intend to use any cash proceeds that we receive upon physical settlement of any forward sale agreement, if physical settlement applies, or upon cash settlement of any forward sale agreement, if we elect cash settlement, for the purposes provided in the immediately preceding paragraph. See “Use of Proceeds.”

Conflicts of Interest The forward purchasers will receive the net proceeds of any sale of borrowed shares of our common stock sold pursuant to this prospectus supplement in connection with any forward sale agreement. Because certain sales agents or their affiliates are expected to receive part of the net proceeds from the sale of shares of our common stock in connection with any forward sale agreement, such sales agents would be deemed to have a conflict of interest under Financial Industry Regulatory Authority, Inc. (“FINRA”) Rule 5121 to the extent such sales agents or affiliates receive at least 5% of the net proceeds of the offering. Any sales agent deemed to have a conflict of interest would be required to conduct the distribution of our common stock in accordance with FINRA Rule 5121. If the offering is conducted in accordance with FINRA Rule 5121, such sales agent would not be permitted to confirm a sale to an account over which it exercises discretionary authority without first receiving specific written approval from the account holder. The appointment of a “qualified independent underwriter” (as defined in FINRA Rule 5121) is not necessary for this offering because the shares of common stock being offered have a “bona fide public market” (as defined in FINRA Rule 5121).

See “Use of Proceeds” and “Plan of Distribution (Conflicts of Interest).”

Listing Our common stock is listed on the NYSE under the symbol “ATO.”

Risk Factors Investing in our common stock involves risks. See “Risk Factors” on pageS-3 of this prospectus supplement and other information included and incorporated by reference in this prospectus supplement and the accompanying prospectus for a discussion of the factors you should consider carefully before deciding to invest in our common stock.

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RISK FACTORS

Investing in our common stock involves risks. Our business is influenced by many factors that are difficult to predict and beyond our control and that involve uncertainties that may materially affect our results of operations, financial condition or cash flows, or the value of our common stock. These risks and uncertainties include those described below, as well as in the risk factors and other sections of the documents that are incorporated by reference in this prospectus supplement and the accompanying prospectus, including “Item 1A. Risk Factors” in our Annual Report on Form10-K for the fiscal year ended September 30, 2019. You should carefully consider these risks and uncertainties and all of the information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus before you invest in our common stock.

Settlement provisions contained in a forward sale agreement could result in substantial dilution to our earnings per share and return on equity or result in substantial cash payment obligations.

If we enter into one or more forward sale agreements, the relevant forward purchaser will have the right to accelerate that particular forward sale agreement (with respect to a transaction under that particular forward sale agreement that the relevant forward purchaser determines is affected by such event) and require us to physically settle or, if we so elect and the forward purchaser permits our election, cash settle or net share settle on a date specified by the relevant forward purchaser if:

• the relevant forward purchaser is unable to, or would incur a materially increased cost to, establish, maintain or unwind its hedge position with respect to that particular forward sale agreement;

• the relevant forward purchaser determines that it is unable, after using commercially reasonable efforts, to continue to borrow a number of shares of our common stock equal to the number of shares of our common stock underlying that particular forward sale agreement or that, with respect to borrowing such number of shares of our common stock, it would incur a cost that is greater than the stock borrowing cost specified in that particular forward sale agreement;

• certain ownership thresholds applicable to such forward purchaser, its affiliates and all other persons who may form a beneficial share ownership group or whose ownership positions would be aggregated with such forward purchaser are exceeded;

• a termination event occurs as a result of us declaring a dividend or distribution on our common stock with a cash value in excess of a specified amount per calendar quarter, or with anex-dividend date prior to the anticipatedex-dividend date for such cash dividend;

• the announcement of an extraordinary event (as such term is defined in that particular forward sale agreement and which includes certain mergers and tender offers and the delisting of our common stock) or a transaction that, if consummated, would result in such an extraordinary event; or

• certain other events of default, termination events or other specified events occur, including, among other things, any material misrepresentation made by us in connection with entering into that particular forward sale agreement, our bankruptcy or a change in law (as such terms are defined in that particular forward sale agreement).

A forward purchaser’s decision to exercise its right to accelerate the settlement of a particular forward sale agreement will be made irrespective of our need for capital. In such cases, we could be required to issue and deliver shares of common stock under the physical settlement provisions of that particular forward sale agreement or, if we so elect and the forward purchaser permits our election, net share settlement provisions of that particular forward sale agreement irrespective of our capital needs, which would result in dilution to our earnings per share and return on equity.

We expect that settlement of any forward sale agreement will generally occur no later than the date specified in the particular forward sale agreement. However, any forward sale agreement may be settled earlier

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than that specified date in whole or in part at our option. We expect that each forward sale agreement will be physically settled by delivery of shares of our common stock, unless we elect to cash settle or net share settle a particular forward sale agreement. Upon physical settlement or, if we so elect, net share settlement of a particular forward sale agreement, delivery of shares of our common stock in connection with such physical settlement or (to the extent we are obligated to deliver shares of our common stock) net share settlement will result in dilution to our earnings per share and return on equity. If we elect cash settlement or net share settlement with respect to all or a portion of the shares of common stock underlying a particular forward sale agreement, we expect that the relevant forward purchaser (or an affiliate thereof) will purchase a number of shares of common stock necessary to satisfy its or its affiliate’s obligation to return the shares of common stock borrowed from third parties in connection with sales of shares of our common stock under that forward sale agreement. In addition, the purchase of shares of our common stock in connection with the relevant forward purchaser or its affiliate unwinding its hedge positions could cause the price of our common stock to increase over such time (or prevent a decrease over such time), thereby increasing the amount of cash we would owe to the relevant forward purchaser (or decreasing the amount of cash that the relevant forward purchaser would owe us) upon a cash settlement of the relevant forward sale agreement or increasing the number of shares of common stock we would deliver to the relevant forward purchaser (or decreasing the number of shares of common stock that the relevant forward purchaser would deliver to us) upon net share settlement of the relevant forward sale agreement. In no event will we be party to outstanding forward sale agreements with more than one forward purchaser at any given time, unless the related forward sellers would not be selling shares of our common stock simultaneously and the related forward purchasers would not be required to unwind their respective hedges of our shares of common stock simultaneously. Therefore, if at any time we are party to an outstanding forward sale agreement with a single forward purchaser, then, without the foregoing selling and unwind restrictions, we may enter into additional forward sale agreements with only the same forward purchaser unless and until that outstanding forward sale agreement matures and settles or otherwise terminates.

The forward sale price that we expect to receive upon physical settlement of a particular forward sale agreement will be subject to adjustment on a daily basis based on a floating interest rate factor equal to the overnight bank funding rate less a spread and will be decreased based on amounts related to expected dividends on our common stock during the term of the particular forward sale agreement. If the overnight bank funding rate is less than the spread for the particular forward sale agreement on any day, the interest factor will result in a daily reduction of the applicable forward sale price. If the market value of our common stock during the relevant valuation period under the particular forward sale agreement is above the applicable forward sale price, in the case of cash settlement, we would pay the relevant forward purchaser under that particular forward sale agreement an amount in cash equal to the difference or, in the case of net share settlement, we would deliver to the relevant forward purchaser a number of shares of common stock having a value equal to the difference. Thus, we could be responsible for a potentially substantial cash payment in the case of cash settlement of a particular forward sale agreement. See “Plan of Distribution (Conflicts of Interest)—Sales Through Forward Sellers” for information on the forward sale agreements.

In case of our bankruptcy or insolvency, any forward sale agreements will automatically terminate, and we would not receive the expected proceeds from any forward sales of our common stock.

If we file for or consent to a proceeding seeking a judgment in bankruptcy or insolvency or any other relief under any bankruptcy or insolvency law or other similar law affecting creditors’ rights, or we or a regulatory authority with jurisdiction over us presents a petition for ourwinding-up or liquidation, and we consent to such a petition, any forward sale agreements that are then in effect will automatically terminate. If any such forward sale agreement so terminates under these circumstances, we would not be obligated to deliver to the relevant forward purchaser any of our common stock not previously delivered, and the relevant forward purchaser would be discharged from its obligation to pay the applicable forward sale price per share in respect of any of our common stock not previously settled under the applicable forward sale agreement. Therefore, to the extent that there are any shares of our common stock with respect to which any forward sale agreement has not been settled at the

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time of the commencement of any such bankruptcy or insolvency proceedings, we would not receive the relevant forward sale price per share in respect of those shares of our common stock.

There may be future sales or other dilution of our equity, which may materially adversely affect the market price for shares of our common stock.

We are generally not restricted from issuing additional shares of common stock, including any securities that are convertible into or exchangeable for, or that represent the right to receive shares of common stock or any substantially similar securities. The market price for shares of our common stock could materially decline as a result of sales of shares of common stock or similar securities in the market made after such offering or the perception that such sales could occur.

The price and trading volume of our common stock may fluctuate significantly, and you could lose all or part of your investment.

The market price of our common stock on the New York Stock Exchange constantly changes and we expect that will continue. In the future, such market price may become highly volatile and subject to wide fluctuations due to our future performance or external factors. In addition, the trading volume of our common stock may fluctuate and cause significant price variations to occur. Volatility in the market price of our common stock may prevent you from being able to sell your shares at or above the price you paid for your shares of common stock. The market price for our common stock could fluctuate significantly for various reasons, including:

• our operating and financial performance and prospects;

• our quarterly or annual earnings or those of other companies in our industry;

• the public’s reaction to our press releases, other public announcements and filings with the SEC;

• changes in earnings estimates or recommendations by securities analysts who track our common stock;

• market and industry perception of our success, or lack thereof, in pursuing our strategies;

• strategic actions by us or our competitors, such as acquisitions or joint ventures;

• changes in accounting standards, policies, guidance, interpretations or principles;

• arrival and departure of key personnel;

• changes in our capital structure; and

• changes in general market, economic and political conditions in the U.S. and global economies or financial markets.

In recent years, the stock market has experienced significant price and volume fluctuations. This volatility frequently has occurred without regard to the operating performance of the affected companies. Hence, the price of our common stock could fluctuate based upon factors that have little or nothing to do with us, and these fluctuations could materially reduce our share price.

All of our debt obligations have priority over shares of our common stock, which would subordinate your rights to payment as a holder of our common stock in the event of a liquidation, dissolution or winding up.

In any liquidation, dissolution or winding up of Atmos Energy, shares of our common stock would rank below all debt claims against Atmos Energy. As a result, holders of shares of our common stock would not be entitled to receive any payment or other distribution of assets upon the liquidation, dissolution or winding up of Atmos Energy until after our obligations to our debt holders have been satisfied.

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Although we have paid cash dividends on shares of our common stock in the past, we may not pay cash dividends or increase our dividends on shares of our common stock in the future.

Holders of shares of our common stock are entitled to receive only such dividends as our Board of Directors may declare out of funds legally available for such purpose. We have a history of paying dividends to our shareholders when sufficient cash is available. However, future cash dividends will depend upon our results of operations, financial condition, cash requirements, the need to maintain adequate capital levels or increase our dividends and other factors. Also, the amount of cash dividends that may be paid on our common stock is restricted by provisions contained in certain debt agreements. There can be no assurance that we will continue to pay dividends or increase our dividends even if the necessary financial conditions are met and if sufficient cash is available for distribution.

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USE OF PROCEEDS

We intend to use the net proceeds we receive upon the issuance and sale of shares of our common stock by us through the sales agents, after deducting the sales agents’ commissions and our offering expenses, to fund capital spending primarily to enhance the safety and reliability of our system, for general corporate purposes, and to repay short-term debt under our commercial paper program, as needed. We use our commercial paper program to fund ongoing working capital needs, such as our seasonal requirements for gas supply, general corporate liquidity and capital expenditures. At February 11, 2020, our commercial paper balance was $0.

We will not initially receive any proceeds from the sale of borrowed shares of our common stock by the forward sellers, as agents for the forward purchasers, in connection with any forward sale agreement as a hedge of the forward sale agreement. In the event of full physical settlement of a forward sale agreement, which we expect to occur on or prior to the maturity date of the forward sale agreement, we expect to receive aggregate cash proceeds equal to the product of the initial forward sale price under the forward sale agreement and the number of shares of our common stock underlying the forward sale agreement, subject to the price adjustment and other provisions of the forward sale agreement. We intend to use any cash proceeds that we receive upon physical settlement of any forward sale agreement, if physical settlement applies, or upon cash settlement of any forward sale agreement, if we elect cash settlement, for the purposes provided in the immediately preceding paragraph. If, however, we elect to cash settle or net share settle any forward sale agreement, we would expect to receive an amount of proceeds that is significantly lower than the product set forth in the second preceding sentence (in the case of any cash settlement) or will not receive any proceeds (in the case of any net share settlement), and we may owe cash (in the case of any cash settlement) or shares of our common stock (in the case of any net share settlement) to the forward purchaser.

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BUSINESS

Overview

Atmos Energy Corporation, headquartered in Dallas, Texas, and incorporated in Texas and Virginia, is one of the country’s largestnatural-gas-only distributors based on number of customers. We deliver natural gas through regulated sales and transportation arrangements to over three million residential, commercial, public authority and industrial customers in eight states located primarily in the South. We also operate one of the largest intrastate pipelines in Texas based on miles of pipe.

Operating Segments

We manage and review our consolidated operations through the following reportable segments:

• Thedistribution segment is primarily comprised of our regulated natural gas distribution and related sales operations in eight states.

• Thepipeline and storage segment is comprised primarily of the pipeline and storage operations of our Atmos Pipeline-Texas Division and our natural gas transmission operations in Louisiana.

Distribution Segment Overview

The following table summarizes key information about our six regulated natural gas distribution divisions, presented in order of total rate base.

Division	Service Areas	Communities Served		Customer Meters
Mid-Tex	Texas, including the Dallas/Fort Worth Metroplex		550		1,722,424
Kentucky/Mid-States	Kentucky Tennessee Virginia		230		183,450 154,004 24,536
Louisiana	Louisiana		270		365,320
West-Texas	Amarillo, Lubbock, Midland		80		316,844
Mississippi	Mississippi		110		266,727
Colorado-Kansas	Colorado Kansas		170		121,883 136,647

We operate in our service areas under terms ofnon-exclusive franchise agreements granted by the various cities and towns that we serve. At September 30, 2019, we held 1,017 franchises having terms generally ranging from five to 35 years. A significant number of our franchises expire each year, which require renewal prior to the end of their terms. Historically, we have successfully renewed these franchises and believe that we will continue to be able to renew our franchises as they expire.

Revenues in this operating segment are established by regulatory authorities in the states in which we operate. These rates are intended to be sufficient to cover the costs of conducting business, including a reasonable return on invested capital. In addition, we transport natural gas for others through our distribution systems.

Rates established by regulatory authorities often include cost adjustment mechanisms for costs that (i) are subject to significant price fluctuations compared to our other costs, (ii) represent a large component of our cost of service and (iii) are generally outside our control.

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Purchased gas cost adjustment mechanisms represent a common form of cost adjustment mechanism. Purchased gas cost adjustment mechanisms provide a method of recovering purchased gas costs on an ongoing basis without filing a rate case because they provide adollar-for-dollar offset to increases or decreases in the cost of natural gas.

Additionally, some jurisdictions have performance-based ratemaking adjustments to provide incentives to minimize purchased gas costs through improved storage management and use of financial instruments to reduce volatility in gas costs. Under the performance-based ratemaking adjustments, purchased gas costs savings are shared between the Company and its customers.

Our rate strategy focuses on reducing or eliminating regulatory lag, obtaining adequate returns and providing stable, predictable margins, which benefit both our customers and the Company. As a result of our ratemaking efforts in recent years, Atmos Energy has:

• Formula rate mechanisms in place in four states that provide for an annual rate review and adjustment to rates.

• Infrastructure programs in place in the majority of our states that provide for an annual adjustment to rates for qualifying capital expenditures. Through our annual formula rate mechanisms and infrastructure programs, we have the ability to recover approximately 90 percent of our capital expenditures within six months and substantially all of our capital expenditures within twelve months.

• Authorization in tariffs, statute or commission rules that allows us to defer certain elements of our cost of service such as depreciation, ad valorem taxes and pension costs, until they are included in rates.

• Weather normalization adjustment mechanisms in seven states that serve to minimize the effects of weather on approximately 96 percent of our residential and commercial meters.

• The ability to recover the gas cost portion of bad debts in five states.

Pipeline and Storage Segment Overview

Our pipeline and storage segment consists of the pipeline and storage operations of our Atmos Pipeline-Texas Division (“APT”) and our natural gas transmission operations in Louisiana. APT is one of the largest intrastate pipeline operations in Texas with a heavy concentration in the established naturalgas-producing areas of central, northern and eastern Texas, extending into or near the major producing areas of the Barnett Shale, the Texas Gulf Coast and the Permian Basin of West Texas. Through its system, APT provides transportation and storage services to ourMid-Tex Division, other third party local distribution companies, industrial and electric generation customers, marketers and producers. As part of its pipeline operations, APT owns and operates five underground storage reservoirs in Texas.

Revenues earned from transportation and storage services for APT are subject to traditional ratemaking governed by the Railroad Commission of Texas. Rates are updated through periodic filings made under Texas’ Gas Reliability Infrastructure Program (“GRIP”). GRIP allows us to include in our rate base annually approved capital costs incurred in the prior calendar year provided that we file a complete rate case at least once every five years; the most recent of which was completed in August 2017. APT’s existing regulatory mechanisms allow certain transportation and storage services to be provided under market-based rates.

Our natural gas transmission operations in Louisiana are comprised of a21-mile pipeline located in the New Orleans, Louisiana area that is primarily used to aggregate gas supply for our distribution division in Louisiana under a long-term contract and, on a more limited basis, to third parties. The demand fee charged to our Louisiana distribution division for these services is subject to regulatory approval by the Louisiana Public Service Commission. We also manage two asset management plans in Louisiana that serve distribution affiliates of the Company, which have been approved by applicable state regulatory commissions. Generally, these asset management plans require us to share with our distribution customers a significant portion of the cost savings earned from these arrangements.

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Other Regulation

We are regulated by various state or local public utility authorities. We are also subject to regulation by the United States Department of Transportation with respect to safety requirements in the operation and maintenance of our transmission and distribution facilities. In addition, our operations are also subject to various state and federal laws regulating environmental matters. From time to time, we receive inquiries regarding various environmental matters. We believe that our properties and operations substantially comply with, and are operated in substantial conformity with, applicable safety and environmental statutes and regulations. There are no administrative or judicial proceedings arising under environmental quality statutes pending or known to be contemplated by governmental agencies which would have a material adverse effect on us or our operations. Our environmental claims have arisen primarily from former manufactured gas plant sites. The Pipeline and Hazardous Materials Safety Administration (“PHMSA”), within the U.S. Department of Transportation, develops and enforces regulations for the safe, reliable and environmentally sound operation of the pipeline transportation system. The PHMSA pipeline safety statutes provide for states to assume safety authority over intrastate natural gas transmission and distribution pipelines. State pipeline safety programs are responsible for adopting and enforcing the federal and state pipeline safety regulations for intrastate natural gas transmission and distribution pipelines.

The Federal Energy Regulatory Commission (“FERC”) allows, pursuant to Section 311 of the Natural Gas Policy Act (“NGA”), gas transportation services through our APT assets “on behalf of” interstate pipelines or local distribution companies served by interstate pipelines, without subjecting these assets to the jurisdiction of the FERC under the NGA. Additionally, the FERC has regulatory authority over the use and release of interstate pipeline and storage capacity. The FERC also has authority to detect and prevent market manipulation and to enforce compliance with FERC’s other rules, policies and orders by companies engaged in the sale, purchase, transportation or storage of natural gas in interstate commerce. We have taken what we believe are the necessary and appropriate steps to comply with these regulations.

The SEC and the Commodities Futures Trading Commission, pursuant to the Dodd-Frank Act (“Dodd-Frank”), established numerous regulations relating to U.S. financial markets. We enacted procedures and modified existing business practices and contractual arrangements to comply with such regulations. There are, however, some rulemaking proceedings that have not yet been finalized, including those relating to capital and margin rules for(non-cleared) swaps. We do not expect these rules to directly impact our business practices or collateral requirements. However, depending on the substance of these final rules, in addition to certain international regulatory requirements still under development that are similar to Dodd-Frank, our swap counterparties could be subject to additional and potentially significant capitalization requirements. These regulations could motivate counterparties to increase our collateral requirements or cash postings.

Competition

Although our regulated distribution operations are not currently in significant direct competition with any other distributors of natural gas to residential and commercial customers within our service areas, we do compete with other natural gas suppliers and suppliers of alternative fuels for sales to industrial customers. We compete in all aspects of our business with alternative energy sources, including, in particular, electricity. Electric utilities offer electricity as a rival energy source and compete for the space heating, water heating and cooking markets. Promotional incentives, improved equipment efficiencies and promotional rates all contribute to the acceptability of electrical equipment. The principal means to compete against alternative fuels is lower prices, and natural gas historically has maintained its price advantage in the residential, commercial and industrial markets.

Our pipeline and storage operations have historically faced competition from other existing intrastate pipelines seeking to provide or arrange transportation, storage and other services for customers. In the last few years, several new pipelines have been completed, which has increased the level of competition in this segment of our business.

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Distribution, Transmission and Related Assets

At September 30, 2019, in our distribution segment, we owned an aggregate of 70,875 miles of underground distribution and transmission mains throughout our distribution systems. These mains are located on easements orrights-of-way. We maintain our mains through a program of continuous inspection and repair and believe that our system of mains is in good condition. Through our pipeline and storage segment we owned 5,669 miles of gas transmission lines as well.

Storage Assets

We own underground gas storage facilities in several states to supplement the supply of natural gas in periods of peak demand. At September 30, 2019, the underground gas storage facilities of our distribution segment had a total usable capacity of 13,103,562 million cubic feet (“Mcf”) and a maximum daily delivery capacity of 234,100 Mcf, with the underground gas storage facilities of our pipeline and storage segment having a total usable capacity of 46,494,589 Mcf and a maximum daily delivery capacity of 1,766,000 Mcf.

Additionally, we contract for storage service in underground storage facilities on many of the interstate pipelines serving us to supplement our proprietary storage capacity. The amount of our contracted storage capacity can vary from time to time. At September 30, 2019, we had contracted storage capacity as follows: (i) distribution segment—maximum quantity of 31,633,242 million British Thermal Units (“MMBtu”) and a maximum daily withdrawal quantity of 1,039,233 MMBtu and (ii) pipeline and storage segment—maximum storage quantity of 1,000,000 MMBtu and a maximum daily withdrawal quantity of 47,500 MMBtu.

For more information on our storage assets, see “Item 2. Properties” in our Annual Report on Form10-K for the fiscal year ended September 30, 2019.

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CERTAIN U.S. FEDERAL INCOME TAX CONSIDERATIONS FORNON-U.S. HOLDERS

The following is a general discussion of certain U.S. federal income tax considerations with respect to the ownership and disposition of shares of our common stock applicable tonon-U.S. Holders who acquire such shares in this offering and hold such shares as a capital asset (generally, property held for investment). For purposes of this discussion, a“non-U.S. Holder” generally means a beneficial owner of our common stock that is not, for U.S. federal income tax purposes, any of the following:

• a citizen or resident of the United States;

• a corporation, or other business entity treated as a corporation, created or organized in the United States or under the laws of the United States, any state thereof or the District of Columbia;

• an estate, the income of which is includible in gross income for U.S. federal income tax purposes regardless of its source; or

• a trust if (a) a court within the United States is able to exercise primary supervision over the administration of the trust and one or more U.S. persons have the authority to control all substantial decisions of the trust or (b) such trust has made a valid election to be treated as a U.S. person for U.S. federal income tax purposes.

This discussion is based on current provisions of the Internal Revenue Code of 1986, as amended from time to time (the “Code”), Treasury regulations promulgated thereunder, judicial opinions, published positions of the Internal Revenue Service (the “IRS”), and other applicable authorities, all of which are subject to change (possibly with retroactive effect). This discussion does not address all aspects of U.S. federal income taxation that may be important to a particularnon-U.S. Holder in light of thatnon-U.S. Holder’s individual circumstances, including Medicare taxes imposed on net investment income and the alternative minimum tax, nor does it address any aspect of U.S. federal estate and gift, state, local, ornon-U.S. taxes. This discussion may not apply, in whole or in part, to particularnon-U.S. Holders in light of their individual circumstances or to holders subject to special treatment under the U.S. federal income tax laws, such as:

• insurance companies;

• tax-exempt organizations;

• financial institutions;

• brokers or dealers in securities;

• controlled foreign corporations and corporations that accumulate earnings to avoid U.S. federal income tax;

• passive foreign investment companies;

• non-U.S. Holders that hold our common stock as part of a straddle, hedge, conversion transaction or other integrated investment;

• persons that own or are deemed to own, actually or constructively, more than 5% of our common stock for U.S. federal income tax purposes; and

• U.S. expatriates.

If a partnership (or other entity or arrangement treated as a partnership for U.S. federal income tax purposes) holds our common stock, the tax treatment of a partner will generally depend on the status of the partner and the activities of the partnership. Partners of a partnership holding our common stock should consult their tax adviser as to the particular U.S. federal income tax consequences applicable to them.

We have not sought, and will not seek, any ruling from the IRS or any opinion of counsel with respect to the tax consequences discussed herein, and there can be no assurance that the IRS will not take a position contrary to the tax consequences discussed below or that any position taken by the IRS would not be sustained.

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EACHNON-U.S. HOLDER IS STRONGLY URGED TO CONSULT ITS TAX ADVISER REGARDING THE U.S. FEDERAL, STATE, LOCAL, ANDNON-U.S. INCOME AND OTHER TAX CONSEQUENCES OF ACQUIRING, HOLDING AND DISPOSING OF OUR COMMON STOCK.

Dividends

In general, any distributions we make to anon-U.S. Holder with respect to its shares of our common stock that constitute dividends for U.S. federal income tax purposes will be subject to U.S. withholding tax at a rate of 30% of the gross amount, unless thenon-U.S. Holder is eligible for a reduced rate of withholding tax under an applicable tax treaty and thenon-U.S. Holder provides proper certification of its eligibility for such reduced rate (including providing a valid IRS FormW-8BEN orW-8BEN-E (or other applicable documentation)). A distribution will constitute a dividend for U.S. federal income tax purposes to the extent of our current or accumulated earnings and profits as determined for U.S. federal income tax purposes. Any distribution not constituting a dividend will be treated first as reducing the adjusted basis in thenon-U.S. Holder’s shares of our common stock and, to the extent it exceeds the adjusted basis in thenon-U.S. Holder’s shares of our common stock, as gain from the sale or exchange of such stock.

Dividends we pay to anon-U.S. Holder that are effectively connected with its conduct of a trade or business within the United States (and, if required by an applicable tax treaty, are attributable to a U.S. permanent establishment of suchnon-U.S. Holder) will not be subject to U.S. withholding tax, as described above, if thenon-U.S. Holder complies with applicable certification and disclosure requirements (including providing a valid IRS FormW-8ECI). Instead, such dividends generally will be subject to U.S. federal income tax on a net income basis, in the same manner as if thenon-U.S. Holder were a resident of the United States. Dividends received by a foreign corporation that are effectively connected with its conduct of a trade or business within the United States may also be subject to an additional branch profits tax at a rate of 30% (or such lower rate as may be specified by an applicable tax treaty).

Any distributions we make to anon-U.S. Holder with respect to its shares of our common stock will also be subject to the rules discussed below under the headings “Backup Withholding, Information Reporting and Other Reporting Requirements” and “Foreign Account Tax Compliance Act.”

Gain on Sale or Other Disposition of Common Stock

In general, anon-U.S. Holder will not be subject to U.S. federal income tax on any gain realized upon the sale or other disposition of thenon-U.S. Holder’s shares of our common stock unless:

• the gain is effectively connected with a trade or business carried on by thenon-U.S. Holder within the United States (and, if required by an applicable tax treaty, is attributable to a U.S. permanent establishment of suchnon-U.S. Holder);

• thenon-U.S. Holder is an individual and is present in the United States for 183 days or more in the taxable year of disposition and certain other conditions are met; or

• we are or have been a U.S. real property holding corporation (a “USRPHC”) for U.S. federal income tax purposes at any time within the shorter of the five-year period preceding such disposition or suchnon-U.S. Holder’s holding period of our common stock. Even though we have significant U.S. real estate holdings, the Company believes that it currently does not qualify as a USRPHC for U.S. federal income tax purposes. Even if we are or become a USRPHC at a relevant time, anon-U.S. Holder who at no time actually or constructively owned more than 5% of the common stock generally would not be subject to U.S. federal income tax on the disposition of the common stock, provided that the common stock was regularly traded on an established securities market within the meaning of the applicable Treasury regulations.

Gain that is effectively connected with the conduct of a trade or business in the United States (or so treated) will generally be subject to U.S. federal income tax, net of certain deductions, at regular U.S. federal income tax

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rates. If thenon-U.S. Holder is a foreign corporation, the branch profits tax described above also may apply to such effectively connected gain. An individualnon-U.S. Holder who is subject to U.S. federal income tax because thenon-U.S. Holder was present in the United States for 183 days or more during the year of sale or other disposition of our common stock will generally be subject to a flat 30% tax on the gain derived from such sale or other disposition, which may be offset by U.S.-source capital losses (assuming certain requirements are met, including timely filing of U.S. federal income tax returns with respect to such losses).Non-U.S. Holders should consult their tax advisers regarding the application of these rules to them, including if we are or become a USRPHC. Any sale or other disposition with respect to anon-U.S. Holder’s shares of our common stock will also be subject to the rules discussed below under the headings “Backup Withholding, Information Reporting and Other Reporting Requirements” and “Foreign Account Tax Compliance Act.”

Backup Withholding, Information Reporting and Other Reporting Requirements

We must report annually to the IRS, and to eachnon-U.S. Holder, the amount of dividends paid to, and the tax withheld with respect to, eachnon-U.S. Holder. These reporting requirements apply regardless of whether withholding was reduced or eliminated by an applicable tax treaty. Copies of this information reporting may also be made available under the provisions of a specific tax treaty or agreement with the tax authorities in the country in which thenon-U.S Holder resides or is established.

Anon-U.S. Holder will generally be subject to backup withholding for dividends on our common stock paid to such holder (at the applicable rate), unless suchnon-U.S. Holder certifies under penalties of perjury that, among other things, it is anon-U.S. Holder (and the payor does not have actual knowledge or reason to know that such holder is a U.S. person), and otherwise complies with all applicable legal requirements.

Information reporting and backup withholding generally are not required with respect to the amount of any proceeds from the sale or other disposition of our common stock by anon-U.S. Holder outside the United States through a foreign office of a foreign broker that does not have certain specified connections to the United States. However, if anon-U.S. Holder sells or otherwise disposes its shares of our common stock through a U.S. broker or the U.S. office of a foreign broker, the broker will generally be required to report the amount of proceeds paid to thenon-U.S. Holder to the IRS and also backup withhold on that amount, unless suchnon-U.S. Holder provides appropriate certification to the broker of its status as anon-U.S. person or otherwise establishes an exemption (and the payor does not have actual knowledge or reason to know that such holder is a U.S. person). Information reporting will also apply if anon-U.S. Holder sells its shares of our common stock through a foreign broker deriving more than a specified percentage of its income from U.S. sources or having certain other connections to the United States, unless such broker has documentary evidence in its records that suchnon-U.S. Holder is anon-U.S. person and certain other conditions are met, or suchnon-U.S. Holder otherwise establishes an exemption (and the payor does not have actual knowledge or reason to know that such holder is a U.S. person).

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules from a payment to anon-U.S. Holder can be credited against thenon-U.S. Holder’s U.S. federal income tax liability, if any, or refunded, provided that the required information is furnished to the IRS in a timely manner.Non-U.S. Holders should consult their tax advisers regarding the application of the information reporting and backup withholding rules to them.

Foreign Account Tax Compliance Act

Withholding taxes may be imposed under Sections 1471 to 1474 of the Code, the Treasury regulations promulgated thereunder and other official guidance (commonly referred to as “FATCA”) on certain types of payments made tonon-U.S. financial institutions and certain othernon-U.S. entities. Specifically, a 30% withholding tax may be imposed on dividends on, or gross proceeds from the sale or other disposition of, our common stock paid to a “foreign financial institution” or a“non-financial foreign entity” (each as defined in the

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Code), unless those entities comply with certain requirements under the Code and applicable Treasury regulations, which requirements may be modified by an “intergovernmental agreement” entered into between the United States and an applicable foreign country. Future Treasury regulations or other official guidance may modify these requirements.

Under the applicable Treasury regulations, withholding under FATCA generally applies to payments of dividends on our common stock. Pursuant to proposed regulations, the Treasury Department has indicated its intent to eliminate the requirements under FATCA of withholding on gross proceeds from the sale or other disposition of certain financial instruments (which would include our stock). The Treasury Department has indicated that taxpayers may rely on these proposed regulations pending their finalization.

Any applicable FATCA withholding tax will apply to all withholdable payments without regard to whether the beneficial owner of the payment would otherwise be entitled to an exemption from imposition of withholding tax pursuant to an applicable tax treaty with the United States or U.S. domestic law. Prospective investors should consult their tax advisers regarding the potential application of withholding under FATCA to their investment in our common stock.

The U.S. federal tax discussion set forth above is included for general information only and may not be applicable depending upon a particularnon-U.S. Holder’s particular situation. Holders should consult their tax advisers with respect to the tax consequences to them of the purchase, ownership and disposition of the stock, including the tax consequences under state, local, foreign and other tax laws and the possible effects of changes in U.S. federal or other tax laws.

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PLAN OF DISTRIBUTION (CONFLICTS OF INTEREST)

We have entered into an equity distribution agreement with Morgan Stanley & Co. LLC, BofA Securities, Inc., BNP Paribas Securities Corp., CIBC World Markets Corp., Credit Agricole Securities (USA) Inc., Goldman Sachs & Co. LLC, J.P. Morgan Securities LLC, Mizuho Securities USA LLC, MUFG Securities Americas Inc., SunTrust Robinson Humphrey, Inc., TD Securities (USA) LLC and Wells Fargo Securities, LLC as our sales agents (the “sales agents”), under which we may offer and sell from time to time shares of common stock having an aggregate offering price of up to $1,000,000,000. We will file the equity distribution agreement as an exhibit to a Current Report on Form8-K, which will be incorporated by reference in this prospectus supplement. The sales, if any, of shares of common stock made under the equity distribution agreement will be made by means of ordinary brokers’ transactions on the New York Stock Exchange (the “NYSE”) at market prices, in block transactions, or as otherwise as agreed upon by the sales agents and us. The sales agents will not engage in any transactions that stabilize the price of our common stock. Further, the equity distribution agreement provides that, in addition to the issuance and sale of shares of our common stock by us through the sales agents, we may deliver instructions to such sales agents specifying that the applicable sales agent, as a forward seller, use commercially reasonable efforts to sell, from time to time, shares of our common stock borrowed by the applicable forward purchaser in connection with one or more forward sale agreements as described below. In no event will the aggregate number of shares of our common stock sold through the sales agents, each as an agent for us, and by each forward seller, under the equity distribution agreement have an aggregate sales price in excess of $1,000,000,000.

Under the terms of the equity distribution agreement, we also may sell shares of common stock to one or more of our sales agents as principal for its own account at a price agreed upon at the time of sale. If we sell shares of common stock to a sales agent as principal, we will enter into a separate agreement with the sales agent, and we will describe this agreement in a separate prospectus supplement or pricing supplement.

The offering of common stock pursuant to the equity distribution agreement will terminate upon the earlier of (1) the sale of all common stock subject to the equity distribution agreement or (2) the termination of the equity distribution agreement by us or by each of the sales agents.

In connection with the sale of the common stock on our behalf, each of the sales agents may be deemed to be an “underwriter” within the meaning of the Act, and the compensation paid to the sales agents may be deemed to be underwriting commissions or discounts. We have agreed to provide indemnification and contribution to the sales agents against certain liabilities, including civil liabilities under the Securities Act.

We intend to report to the SEC at least quarterly (1) the number of shares of our common stock sold through the sales agents in connection withat-the-market sales as described below under “—Sales Through Sales Agents,” (2) the number of borrowed shares of our common stock sold by the forward sellers, as agents for the forward purchasers, in connection with forward sale agreements as described below under “—Sales Through Forward Sellers” and (3) the net proceeds received by us and the compensation paid by us to the sales agents in connection with transactions described in clauses (1) and (2).

Sales Through Sales Agents

We will designate the maximum amount of common stock to be sold through the sales agents on a daily basis or otherwise as we and the sales agents agree and the minimum price per share at which such common stock may be sold. Subject to the terms and conditions of the equity distribution agreement, the sales agents will use their reasonable efforts to sell on our behalf all of the designated shares of common stock. We may instruct the sales agents not to sell any common stock if the sales cannot be effected at or above the price designated by us in any such instruction. We or the sales agents may suspend the offering of common stock at any time and from time to time by notifying the other party.

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The sales agents will provide to us written confirmation following the close of trading on the NYSE each day in which shares of common stock are sold under the equity distribution agreement. Each confirmation will include the number of shares sold on that day, the gross sales proceeds, the net proceeds to us (after regulatory transaction fees, if any, but before other expenses) and the compensation payable by us to the sales agents.

We will pay each sales agent a commission of 1.00% of the gross sales price per share of common stock sold through it as our agent under the equity distribution agreement. In addition, we have agreed to reimburse the sales agents for certain reasonable documentedout-of-pocket expenses, including the reasonable fees, disbursements and expenses of their counsel, in connection with entering into the applicable equity distribution agreement and performing its obligations thereunder.

Settlement for sales of common stock will occur on the second business day following the date on which any sales were made in return for payment of the net proceeds to us. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

If we or any of the sales agents have reason to believe that shares of our common stock are no longer “actively-traded securities” as defined under Rule 101(c)(1) of Regulation M under the Exchange Act, that party will promptly notify the others and sales of common stock pursuant to the equity distribution agreement or any terms agreement will be suspended until in our collective judgment Rule 101(c)(1) or another exemptive provision has been satisfied.

Sales Through Forward Sellers

From time to time during the term of the equity distribution agreement, and subject to the terms and conditions set forth therein, we may enter into one or more forward sale agreements with each of Morgan Stanley & Co. LLC, BNP Paribas, Canadian Imperial Bank of Commerce, Credit Agricole Corporate and Investment Bank c/o Credit Agricole Securities (USA) Inc., as Agent, Goldman Sachs & Co. LLC, JPMorgan Chase Bank, National Association, Bank of America N.A., Mizuho Securities USA LLC, MUFG Securities EMEA plc, The Toronto-Dominion Bank and Wells Fargo Bank, National Association or their respective affiliates, as forward purchaser, and deliver to the applicable sales agent or its respective affiliate a related transaction confirmation under the equity distribution agreement in its capacity as forward seller thereunder. Upon receipt by a forward purchaser of a transaction confirmation from us requesting that it execute sales of borrowed shares of common stock as a forward seller in connection with the applicable forward sale agreement and subject to the terms and conditions of the equity distribution agreement, the relevant forward purchaser will attempt to borrow, and the relevant forward seller will use commercially reasonable efforts consistent with its normal trading and sales practices and applicable laws and regulations to sell, the relevant shares of our common stock to hedge the relevant forward purchaser’s exposure under that particular forward sale agreement. We or the relevant forward seller may immediately suspend the offering of our common stock at any time upon proper notice to the other. In no event will we be party to outstanding forward sale agreements with more than one forward purchaser at any given time unless the related forward sellers would not be selling shares of our common stock simultaneously and the related forward purchasers would not be required to unwind their respective hedges of our shares of common stock simultaneously. Therefore, if at any time we are party to an outstanding forward sale agreement with a single forward purchaser, then, without the foregoing selling and unwind restrictions, we may enter into additional forward sale agreements with only the same forward purchaser unless and until that outstanding forward sale agreement matures and settles or otherwise terminates.

We expect that settlement between the relevant forward purchaser and forward seller of sales of borrowed shares of our common stock, as well as the settlement between the relevant forward seller and buyers of such shares of our common stock in the market, will generally occur on the second trading day following each date the sales are made or such earlier day as required by SEC rule or industry practice, unless another date shall be agreed to in writing by us and the relevant forward seller. The obligation of the relevant forward seller under the equity distribution agreement to execute such sales of our common stock is subject to a number of conditions, which each forward seller reserves the right to waive in its sole discretion.

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In connection with each forward sale agreement, we will pay the relevant forward seller, in the form of a reduced initial forward sale price payable by the relevant forward purchaser under the related forward sale agreement, commissions of 1.00% of the sales prices of all borrowed shares of common stock sold during the applicable forward hedge selling period by it as a forward seller. We refer to this commission rate as the forward selling commission. The forward hedge selling period will be the period of one trading day as specified in the relevant transaction confirmation and the forward sale agreement related thereto.

The forward sale price per share under each forward sale agreement will initially equal the product of (1) an amount equal to one minus the applicable forward selling commission and (2) the volume-weighted average price per share at which the borrowed shares of common stock were sold pursuant to the equity distribution agreement by the relevant forward seller. Thereafter, the forward sale price will be subject to adjustment as described below.

The forward sale agreements will provide that the forward sale price, as well as the sales prices used to calculate the initial forward sale price, will be subject to increase or decrease based on a floating interest rate factor equal to the overnight bank funding rate, less a spread, and subject to decrease by amounts related to expected dividends on our common stock during the term of the particular forward sale agreement. If the overnight bank funding rate is less than the spread for the particular forward sale agreement on any day, the interest factor will result in a daily reduction of the forward sale price. Unless the overnight bank funding rate increases substantially prior to the settlement of any particular forward sale agreement, we would expect to receive less than the initial forward sale price per share upon physical settlement of that particular forward sale agreement.

Before settlement of a particular forward sale agreement, we expect that the shares of our common stock issuable upon settlement of that particular forward sale agreement will be reflected in our diluted earnings per share, return on equity and dividends per share calculations using the treasury stock method. Under this method, the number of shares of our common stock used in calculating diluted earnings per share, return on equity and dividends per share is deemed to be increased by the excess, if any, of the number of shares of our common stock that would be issued upon full physical settlement of that particular forward sale agreement over the number of shares of our common stock that could be purchased by us in the market (based on the average market price during the relevant period) using the proceeds receivable upon full physical settlement (based on the adjusted forward sale price at the end of the relevant reporting period). Consequently, before physical or net share settlement of a particular forward sale agreement and subject to the occurrence of certain events, we anticipate there will be no dilutive effect on our earnings per share, except during periods when the average market price of our common stock is above the applicable forward sale price.

Except under limited circumstances described below, we have the right to elect physical, cash or net share settlement under any forward sale agreement. Although we expect to settle any forward sale agreement entirely by delivering shares of our common stock in connection with full physical settlement, we may, subject to certain conditions, elect cash settlement or net share settlement for all or a portion of our obligations under a particular forward sale agreement if we conclude that it is in our interest to do so. For example, we may conclude that it is in our interest to cash settle or net share settle a particular forward sale agreement if we have no then-current use for all or a portion of the net proceeds that we would receive upon physical settlement. In addition, subject to certain conditions, we may elect to accelerate the settlement of all or a portion of the number of shares of our common stock underlying a particular forward sale agreement.

If we elect to physically settle any forward sale agreement by issuing and delivering shares of our common stock, we will receive an amount of cash from the relevant forward purchaser equal to the product of the forward sale price per share under that particular forward sale agreement and the number of shares of our common stock underlying the particular forward sale agreement subject to physical settlement. In the event that we elect to cash settle, the settlement amount will be generally related to (1) (a) the weighted average price at which the relevant forward purchaser or its affiliate purchases shares of our common stock during the relevant valuation period for

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such settlement under that particular forward sale agreement minus (b) the applicable forward sale price; multiplied by (2) the number of shares of our common stock underlying the particular forward sale agreement subject to cash settlement. In the event we elect to net share settle, the settlement amount will be generally related to (1) (a) the weighted average price at which the relevant forward purchaser or its affiliate purchases shares of our common stock during the relevant valuation period for such settlement under that particular forward sale agreement minus (b) the applicable forward sale price; multiplied by (2) the number of shares of our common stock underlying the particular forward sale agreement subject to such net share settlement. If this settlement amount is a negative number, the relevant forward purchaser will pay us the absolute value of that amount (in the case of cash settlement) or deliver to us a number of shares of our common stock having a value equal to the absolute value of such amount (in the event of net share settlement). If this settlement amount is a positive number, we will pay the relevant forward purchaser that amount (in the case of cash settlement) or deliver to the relevant forward purchaser a number of shares of our common stock having a value equal to such amount (in the event of net share settlement). In connection with any cash settlement or net share settlement, we would expect the relevant forward purchaser or its affiliate to purchase shares of our common stock in secondary market transactions for delivery to third-party stock lenders in order to close out its, or its affiliate’s, hedge position in respect of that particular forward sale agreement. The purchase of shares of our common stock in connection with the relevant forward purchaser or its affiliate unwinding its hedge positions could cause the price of our common stock to increase over time (or prevent a decrease over time), thereby increasing the amount of cash we owe to the relevant forward purchaser (or decreasing the amount of cash that the relevant forward purchaser owes us) upon cash settlement or increasing the number of shares of our common stock that we are obligated to deliver to the relevant forward purchaser (or decreasing the number of shares of our common stock that the relevant forward purchaser is obligated to deliver to us) upon net share settlement of the particular forward sale agreement. See “Risk Factors.”

A forward purchaser will have the right to accelerate its forward sale agreement (with respect to a transaction under the particular forward sale agreement that the relevant forward purchaser determines is affected by such event) and require us to physically settle or, if we so elect and the forward purchaser permits our election, cash settle or net share settle on a date specified by the relevant forward purchaser if:

• the relevant forward purchaser is unable to, or would incur a materially increased cost to, establish, maintain or unwind its hedge position with respect to the particular forward sale agreement;

• the relevant forward purchaser determines that it is unable, after using commercially reasonable efforts, to continue to borrow a number of shares of our common stock equal to the number of shares of our common stock underlying the particular forward sale agreement or that, with respect to borrowing such number of shares of our common stock, it would incur a cost that is greater than the stock borrowing cost specified in the particular forward sale agreement;

• certain ownership thresholds applicable to such forward purchaser, its affiliates and all other persons who may form a beneficial share ownership group or whose ownership positions would be aggregated with such forward purchaser are exceeded;

• a termination event occurs as a result of us declaring a dividend or distribution on our common stock with a cash value in excess of a specified amount per calendar quarter or with anex-dividend date prior to the anticipatedex-dividend date for such cash dividend;

• the announcement of an extraordinary event (as such term is defined in the particular forward sale agreement and which includes certain mergers and tender offers and the delisting of our common stock) or a transaction that, if consummated, would result in an extraordinary event; or

• certain other events of default, termination events or other specified events occur, including, among other things, any material misrepresentation made by us in connection with entering into the particular forward sale agreement, our bankruptcy or a change in law (as such terms are defined in the particular forward sale agreement).

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The relevant forward purchaser’s decision to exercise its right to accelerate the settlement of the particular forward sale agreement will be made irrespective of our need for capital. In such cases, we could be required to issue and deliver shares of our common stock under the physical settlement provisions of the particular forward sale agreement or, if we so elect and the relevant forward purchaser so permits our election, the net share settlement provisions of the particular forward sale agreement irrespective of our capital needs, which would result in dilution to our earnings per share, return on equity and dividends per share. In addition, upon certain events of bankruptcy, insolvency or reorganization relating to us, the particular forward sale agreement will terminate without further liability of either party. Following any such termination, we would not issue any shares of our common stock or receive any proceeds pursuant to the particular forward sale agreement. See “Risk Factors.”

Conflicts of Interest

The sales agents and their respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory investment management, investment research, principal investment, hedging, financing and brokerage activities. In the ordinary course of business, certain of the sales agents or their respective affiliates have provided and may in the future provide commercial, financial advisory or investment banking services for us and our subsidiaries for which they have received or will receive customary compensation. For example, affiliates of certain of the sales agents are lenders under our revolving credit facilities and dealers under our commercial paper program. To the extent we use the proceeds from this offering to repay any indebtedness under our revolving credit facilities or commercial paper program, such affiliates of certain sales agents will receive a portion of the proceeds from this offering.

In the ordinary course of their various business activities, the sales agents and their respective affiliates have made or held, and may in the future make or hold, a broad array of investments including serving as counterparties to certain derivative and hedging arrangements, and may have actively traded, and, in the future may actively trade, debt and equity securities (or related derivative securities), and financial instruments (including bank loans) for their own account and for the accounts of their customers and may have in the past and at any time in the future hold long and short positions in such securities and instruments. Such investment and securities activities may have involved, and in the future may involve, securities and instruments of us or our subsidiaries. The sales agents and their respective affiliates may also communicate independent investment recommendations, market color or trading ideas and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

The forward purchasers will receive the net proceeds of any sale of borrowed shares of our common stock sold pursuant to this prospectus supplement in connection with any forward sale agreement. Because certain sales agents or their affiliates are expected to receive part of the net proceeds from the sale of shares of our common stock in connection with any forward sale agreement, such sales agents would be deemed to have a conflict of interest under FINRA Rule 5121 to the extent such sales agents or affiliates receive at least 5% of the net proceeds of the offering. Any sales agent deemed to have a conflict of interest would be required to conduct the distribution of our common stock in accordance with FINRA Rule 5121. If the offering is conducted in accordance with FINRA Rule 5121, such sales agent would not be permitted to confirm a sale to an account over which it exercises discretionary authority without first receiving specific written approval from the account holder. The appointment of a “qualified independent underwriter” (as defined in FINRA Rule 5121) is not necessary for this offering because the shares of common stock being offered have a “bona fide public market” (as defined in FINRA Rule 5121).

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LEGAL MATTERS

The validity of the shares of common stock offered hereby will be passed upon for us by Gibson, Dunn & Crutcher LLP and Hunton Andrews Kurth LLP. Certain legal matters in connection with this offering will be passed upon for the sales agents by Shearman & Sterling LLP, New York, New York.

EXPERTS

The consolidated financial statements of Atmos Energy appearing in Atmos Energy’s Annual Report (Form10-K) for the year ended September 30, 2019 (including the schedule appearing therein), and the effectiveness of Atmos Energy’s internal control over financial reporting as of September 30, 2019 have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

With respect to the unaudited condensed consolidated interim financial information of Atmos Energy for the three-month periods ended December 31, 2019 and December 31, 2018, incorporated by reference in this Prospectus, Ernst & Young LLP reported that they have applied limited procedures in accordance with professional standards for a review of such information. However, their separate report dated February 4, 2020, included in Atmos Energy’s Quarterly Report on Form 10-Q for the quarter ended December 31, 2019, and incorporated by reference herein, states that they did not audit and they do not express an opinion on that interim financial information. Accordingly, the degree of reliance on their report on such information should be restricted in light of the limited nature of the review procedures applied. Ernst & Young LLP is not subject to the liability provisions of Section 11 of the Securities Act of 1933 (the “Act”) for their report on the unaudited interim financial information because that report is not a “report” or a “part” of the Registration Statement prepared or certified by Ernst & Young LLP within the meaning of Sections 7 and 11 of the Act.

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INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” information in this prospectus supplement or the accompanying base prospectus that we have filed with the SEC. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be part of this prospectus supplement and the accompanying base prospectus, except for any information that is superseded by information that is included directly in this prospectus supplement or the accompanying base prospectus relating to an offering of our securities.

We incorporate by reference into this prospectus supplement the documents listed below and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of our offering of securities. These additional documents include periodic reports, such as annual reports on Form10-K and quarterly reports on Form10-Q, and current reports on Form8-K (other than information furnished under Items 2.02 and 7.01 or corresponding information furnished under Item 9.01 as an exhibit, which is deemed not to be incorporated by reference in this prospectus supplement), as well as proxy statements (other than information identified in them as not incorporated by reference). You should review these filings as they may disclose a change in our business, prospects, financial condition or other affairs after the date of this prospectus supplement.

This prospectus supplement incorporates by reference the documents listed below that we have filed with the SEC but have not been included or delivered with this document:

• Our annual report onForm10-K for the year ended September 30, 2019;

• The following pages and captioned text contained in ourdefinitive proxy statement for the annual meeting of shareholders on February 5, 2020 and incorporated by reference into our annual report on Form10-K: pages 7 through 14 under the captions“Corporate Governance and Other Board Matters—Independence of Directors” and“—Committees of the Board of Directors,” and“—Related Party Transactions and Review Policy;” pages 18 through 24 under the caption“Proposal One—Election of Directors—Nominees for Director;” pages 25 through 27 under the caption“Director Compensation;” pages 28 through 29 under the captions“Proposal Two—Ratification of Appointment of Independent Registered Public Accounting Firm—Audit and Related Fees” and “—Audit CommitteePre-Approval Policy;” pages 31 through 42 under the caption“Compensation Discussion and Analysis;” pages 43 through 56 under the caption“Named Executive Officer Compensation;” pages 57 through 58 under the caption“Other Executive Compensation Matters;” and pages 59 through 60 under the caption“Beneficial Ownership of Common Stock”;

• Our quarterly report onForm10-Q for the quarter ended December 31, 2019; and

• Our current reports on Form8-K filed onOctober  2, 2019 (two filed on this date) andFebruary 10, 2020.

These documents contain important information about us and our financial condition.

You may obtain a copy of any of these filings, or any of our future filings, from us without charge by requesting it in writing or by telephone at the following address or telephone number:

Atmos Energy Corporation

1800 Three Lincoln Centre

5430 LBJ Freeway

Dallas, Texas 75240

Attention: Jennifer Hills

(972)934-9227

Our website iswww.atmosenergy.com; any information on or connected to our website is not part of this prospectus supplement.

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PROSPECTUS

Atmos Energy Corporation

By this prospectus, we offer up to

$4,000,000,000

of debt securities and common stock.

We will provide specific terms of these securities in supplements to this prospectus. This prospectus may not be used to sell securities unless accompanied by a prospectus supplement. You should read this prospectus and the applicable prospectus supplement carefully before you invest.

Investing in these securities involves risks. See “Risk Factors” on page 3 of this prospectus, in the applicable prospectus supplement and in the documents incorporated by reference.

Our common stock is listed on the New York Stock Exchange under the symbol “ATO.”

Our address is 1800 Three Lincoln Centre, 5430 LBJ Freeway, Dallas, Texas 75240, and our telephone number is(972) 934-9227.

The Securities and Exchange Commission and state securities regulators have not approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

This prospectus is dated February 11, 2020

We have not authorized any other person to provide you with any information or to make any representation that is different from, or in addition to, the information and representations contained in this prospectus or in any of the documents that are incorporated by reference in this prospectus. We take no responsibility for, and can provide no assurances as to the reliability of, any other information that others may give you or representations that others may make. We are not making or soliciting an offer of any securities other than the securities described in this prospectus and any prospectus supplement. You should assume that the information appearing in this prospectus, as well as the information contained in any document incorporated by reference, is accurate as of the date of each such document only, unless the information specifically indicates that another date applies.

TABLE OF CONTENTS

	Page
Cautionary Statement Regarding Forward-Looking Statements		1
Risk Factors		3
Atmos Energy Corporation		3
Securities We May Offer		3
Use of Proceeds		4
Description of Debt Securities		4
Description of Common Stock		20
Plan of Distribution		22
Legal Matters		24
Experts		24
Where You Can Find More Information		24
Incorporation of Certain Documents by Reference		25

The distribution of this prospectus may be restricted by law in certain jurisdictions. You should inform yourself about and observe any of these restrictions. This prospectus does not constitute, and may not be used in connection with, an offer or solicitation by anyone in any jurisdiction in which the offer or solicitation is not authorized, or in which the person making the offer or solicitation is not qualified to do so, or to any person to whom it is unlawful to make the offer or solicitation.

The terms “we,” “our,” “us,” and “Atmos Energy” refer to Atmos Energy Corporation and its subsidiaries unless the context suggests otherwise. The term “you” refers to a prospective investor.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Statements contained or incorporated by reference in this prospectus that are not statements of historical fact are “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”). Forward-looking statements are based on management’s beliefs as well as assumptions made by, and information currently available to, management. Because such statements are based on expectations as to future results and are not statements of fact, actual results may differ materially from those stated. Important factors that could cause future results to differ include, but are not limited to:

• state and local regulatory trends and decisions, including the impact of rate proceedings before various state regulatory commissions;

• increased federal regulatory oversight and potential penalties;

• possible increased federal, state and local regulation of the safety of our operations;

• possible significant costs and liabilities resulting from pipeline integrity and other similar programs and related repairs;

• the inherent hazards and risks involved in distributing, transporting and storing natural gas;

• the capital-intensive nature of our business;

• our ability to continue to access the credit and capital markets to execute our business strategy;

• market risks beyond our control affecting our risk management activities, including commodity price volatility, counterparty performance or creditworthiness and interest rate risk;

• the concentration of our operations in Texas;

• the impact of adverse economic conditions on our customers;

• changes in the availability and price of natural gas;

• the availability and accessibility of contracted gas supplies, interstate pipeline and/or storage services;

• increased competition from energy suppliers and alternative forms of energy;

• adverse weather conditions;

• increased costs of providing health care benefits, along with pension and postretirement health care benefits and increased funding requirements;

• the inability to continue to hire, train and retain operational, technical and managerial personnel;

• the impact of climate change;

• the impact of greenhouse gas emissions or other legislation or regulations intended to address climate change;

• increased dependence on technology that may hinder the Company’s business if such technologies fail;

• the threat of cyber-attacks or acts of cyber-terrorism that could disrupt our business operations and information technology systems or result in the loss or exposure of confidential or sensitive customer, employee or Company information;

• natural disasters, terrorist activities or other events; and

• other risks and uncertainties discussed in this prospectus, any accompanying prospectus supplement and our other filings with the Securities and Exchange Commission (the “SEC”).

All of these factors are difficult to predict and many are beyond our control. Accordingly, while we believe our forward-looking statements to be reasonable, there can be no assurance that they will approximate actual

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experience or that the expectations derived from them will be realized. When used in our documents or oral presentations, the words “anticipate,” “believe,” “estimate,” “expect,” “forecast,” “goal,” “intend,” “objective,” “plan,” “projection,” “seek,” “strategy” or similar words are intended to identify forward-looking statements. We undertake no obligation to update or revise any of our forward-looking statements, whether as a result of new information, future events or otherwise.

For additional factors you should consider generally and when evaluating these forward-looking statements, please see “Risk Factors” below, “Item 1A. Risk Factors” and “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations” in our Annual Report on Form10-K for the fiscal year ended September 30, 2019. See also “Incorporation of Certain Documents by Reference” on page 25 of this prospectus, as well as the applicable prospectus supplement.

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RISK FACTORS

Investing in our debt securities or our common stock involves risks. Our business is influenced by many factors that are difficult to predict and beyond our control and that involve uncertainties that may materially affect our results of operations, financial condition or cash flows, or the value of these securities. These risks and uncertainties include those described in the risk factors and other sections of the documents that are incorporated by reference in this prospectus. Subsequent prospectus supplements may contain a discussion of additional risks applicable to an investment in us and the particular type of securities we are offering under the prospectus supplements. You should carefully consider all of the information contained in or incorporated by reference in this prospectus or in the applicable prospectus supplement before you invest in our debt securities or common stock.

ATMOS ENERGY CORPORATION

Atmos Energy Corporation, headquartered in Dallas, Texas, and incorporated in Texas and Virginia, is one of the country’s largestnatural-gas-only distributors based on number of customers. We deliver natural gas through regulated sales and transportation arrangements to over three million residential, commercial, public authority and industrial customers in eight states located primarily in the South. We also operate one of the largest intrastate pipelines in Texas based on miles of pipe.

We manage and review our consolidated operations through the following reportable segments:

• Thedistribution segment is primarily comprised of our regulated natural gas distribution and related sales operations in eight states.

• Thepipeline and storage segment is comprised primarily of the pipeline and storage operations of our Atmos Pipeline—Texas division and our natural gas transmission operations in Louisiana.

SECURITIES WE MAY OFFER

Types of Securities

The types of securities that we may offer and sell from time to time by this prospectus are:

• debt securities, which we may issue in one or more series and which may include provisions regarding conversion of the debt securities into our common stock; and

• common stock.

The aggregate initial offering price of all securities sold will not exceed $4,000,000,000. We will determine when we sell securities, the amounts of securities we will sell and the prices and other terms on which we will sell them. We may sell securities to or through underwriters, through agents or dealers or directly to purchasers. The offer and sale of securities by this prospectus is subject to receipt of satisfactory regulatory approvals in three states, all of which have been received and are currently in effect.

Prospectus Supplements

This prospectus provides you with a general description of the debt securities and common stock we may offer. Each time we offer securities, we will provide a prospectus supplement that will contain specific information about the terms of the offering. The prospectus supplement may also add to or change information contained in this prospectus. In that case, the prospectus supplement should be read as superseding this prospectus.

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In each prospectus supplement, which will be attached to the front of this prospectus, we will include, among other things, the following information:

• the type and amount of securities which we propose to sell;

• the initial public offering price of the securities;

• the names of the underwriters, agents or dealers, if any, through or to which we will sell the securities;

• the compensation, if any, of those underwriters, agents or dealers;

• if applicable, information about the securities exchanges or automated quotation systems on which the securities will be listed or traded;

• material United States federal income tax considerations applicable to the securities, where necessary; and

• any other material information about the offering and sale of the securities.

For more details on the terms of the securities, you should read the exhibits filed with our registration statement, of which this prospectus is a part. You should also read both this prospectus and the applicable prospectus supplement, together with additional information described under the heading “Where You Can Find More Information.”

USE OF PROCEEDS

Except as may otherwise be stated in the applicable prospectus supplement, we intend to use the net proceeds from the sale of the securities that we may offer and sell from time to time by this prospectus for general corporate purposes, including for working capital, repaying indebtedness and funding capital projects and other growth.

DESCRIPTION OF DEBT SECURITIES

We may issue debt securities from time to time in one or more distinct series. This section summarizes the material terms that we anticipate will be common to all series of debt securities. Please note that the terms of any series of debt securities that we may offer may differ significantly from the common terms described in this prospectus. Many of the other terms of any series of debt securities that we offer, and any differences from the common terms described in this prospectus, will be described in the prospectus supplement for such securities to be attached to the front of this prospectus.

As required by U.S. federal law for all bonds and notes of companies that are publicly offered, a document called an indenture will govern any debt securities that we issue. An indenture is a contract between us and a financial institution acting as trustee on behalf of the purchasers of the debt securities. We have entered into an indenture with U.S. Bank National Association, as trustee (the “indenture”), which is subject to the Trust Indenture Act of 1939. The trustee under the indenture has the following two main roles:

• the trustee can enforce your rights against us if we default; there are some limitations on the extent to which the trustee acts on your behalf, which are described later in this prospectus; and

• the trustee will perform certain administrative duties for us, which include sending you interest payments and notices.

As this section is a summary of some of the terms of the debt securities we may offer under this prospectus, it does not describe every aspect of the debt securities. We urge you to read the indenture and the other

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documents we file with the SEC relating to the debt securities because the indenture for those securities and those other documents, and not this description, will define your rights as a holder of our debt securities. We filed a copy of the indenture with the SEC as an exhibit to our Current Report on Form8-K filed March 26, 2009, and it is incorporated in this prospectus by reference. We may file any such other documents as exhibits to an annual, quarterly or current report that we file with the SEC following their execution. See “Where You Can Find More Information” for information on how to obtain copies of the indenture and any such other documents. References to the “indenture” mean the indenture that will define your rights as a holder of debt securities. Capitalized terms used in this section and not otherwise defined have the meanings set forth in the indenture.

General

The debt securities will be our unsecured obligations. Senior debt securities will rank equally with all of our other unsecured and unsubordinated indebtedness. Subordinated debt securities will rank junior to our senior indebtedness, including our credit facilities.

You should read the prospectus supplement that will describe the following terms of the series of debt securities offered by the prospectus supplement:

• the title of the debt securities and whether the debt securities will be senior debt securities or subordinated debt securities;

• the ranking of the debt securities;

• if the debt securities are subordinated, the terms of subordination;

• the aggregate principal amount of the debt securities, the percentage of their principal amount at which the debt securities will be issued, and the date or dates when the principal of the debt securities will be payable or how those dates will be determined or extended;

• the interest rate or rates, which may be fixed or variable, that the debt securities will bear, if any, how the rate or rates will be determined, and the periods when the rate or rates will be in effect;

• the date or dates from which any interest will accrue or how the date or dates will be determined, the date or dates on which any interest will be payable, whether and the terms under which payment of interest may be deferred, any regular record dates for these payments or how these dates will be determined and the basis on which any interest will be calculated, if other than on the basis of a360-day year of twelve30-day months;

• the place or places, if any, other than or in addition to New York City, of payment, transfer or exchange of the debt securities, and where notices or demands to or upon us in respect of the debt securities may be served;

• any optional redemption provisions and any restrictions on the sources of funds for redemption payments, which may benefit the holders of other securities;

• any sinking fund or other provisions that would obligate us to repurchase or redeem the debt securities;

• whether the amount of payments of principal of, any premium on, or interest on the debt securities will be determined with reference to an index, formula or other method, which could be based on one or more commodities, equity indices or other indices, and how these amounts will be determined;

• any modifications, deletions or additions to the events of default or covenants with respect to the debt securities described in this prospectus;

• if not the principal amount of the debt securities, the portion of the principal amount that will be payable upon acceleration of the maturity of the debt securities or how that portion will be determined;

• any modifications, deletions or additions to the provisions concerning defeasance and covenant defeasance contained in the indenture that will be applicable to the debt securities;

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• any provisions granting special rights to the holders of the debt securities upon the occurrence of specified events;

• if other than the trustee, the name of the paying agent, security registrar or transfer agent for the debt securities;

• if we do not issue the debt securities in book-entry form only to be held by The Depository Trust Company, as depository, whether we will issue the debt securities in certificated form or the identity of any alternative depository;

• the person to whom any interest in a debt security will be payable, if other than the registered holder at the close of business on the regular record date;

• the denomination or denominations in which the debt securities will be issued, if other than denominations of $2,000 or any integral multiple of $1,000 in excess thereof;

• any provisions requiring us to pay Additional Amounts on the debt securities to any holder who is not a United States person in respect of any tax, assessment or governmental charge and, if so, whether we will have the option to redeem the debt securities rather than pay the Additional Amounts;

• whether the debt securities will be convertible into or exchangeable for other debt securities or common shares, and, if so, the terms and conditions upon which the debt securities will be so convertible or exchangeable, including the initial conversion or exchange price or rate or the method of calculation, how and when the conversion price or exchange ratio may be adjusted, whether conversion or exchange is mandatory, at the option of the holder or at our option, the conversion or exchange period and any other provision related to the debt securities; and

• any other material terms of the debt securities or the indenture, which may not be consistent with the terms set forth in this prospectus.

For purposes of this prospectus, any reference to the payment of principal of, any premium on, or interest on the debt securities will include Additional Amounts if required by the terms of the debt securities.

The indenture does not limit the amount of debt securities that we are authorized to issue from time to time. The indenture also provides that there may be multiple series of debt securities issued thereunder and more than one trustee thereunder, each for one or more series of debt securities. If a trustee is acting under the indenture with respect to more than one series of debt securities, the debt securities for which it is acting would be treated as if issued under separate indentures. If there is more than one trustee under the indenture, the powers and trust obligations of each trustee will apply only to the debt securities of the separate series for which it is trustee.

We may issue debt securities with terms different from those of debt securities already issued. Without the consent of the holders of the outstanding debt securities, we may reopen a previous issue of a series of debt securities and issue additional debt securities of that series unless the reopening was restricted when we created that series.

There is no requirement that we issue debt securities in the future under the indenture, and we may use other indentures or documentation, containing different provisions in connection with future issues of other debt securities.

We may issue the debt securities as “original issue discount securities,” which are debt securities, including anyzero-coupon debt securities, that are issued and sold at a discount from their stated principal amount. Original issue discount securities provide that, upon acceleration of their maturity, an amount less than their principal amount will become due and payable. We will describe the U.S. federal income tax consequences and other considerations applicable to original issue discount securities in any prospectus supplement relating to them.

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Holders of Debt Securities

Book-Entry Holders. We will issue debt securities in book-entry form only, unless we specify otherwise in the applicable prospectus supplement. This means the debt securities will be represented by one or more global securities registered in the name of a financial institution that holds them as depository on behalf of other financial institutions that participate in the depository’s book-entry system. These participating institutions, in turn, hold beneficial interests in the debt securities on behalf of themselves or their customers.

Under the indenture, we will recognize as a holder only the person in whose name a debt security is registered. Consequently, for debt securities issued in global form, we will recognize only the depository as the holder of the debt securities and we will make all payments on the debt securities to the depository. The depository passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depository and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the debt securities. As a result, you will not own the debt securities directly. Instead, you will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depository’s book-entry system or holds an interest through a participant. As long as the debt securities are issued in global form, you will be an indirect holder, and not a holder, of the debt securities.

Street Name Holders. In the future we may terminate a global security or issue debt securities initially innon-global form. In these cases, you may choose to hold your debt securities in your own name or in “street name.” Debt securities held in street name would be registered in the name of a bank, broker or other financial institution that you choose, and you would hold only a beneficial interest in those debt securities through an account you maintain at that institution.

For debt securities held in street name, we will recognize only the intermediary banks, brokers and other financial institutions in whose names the debt securities are registered as the holders of those debt securities, and we will make all payments on those debt securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. If you hold debt securities in street name you will be an indirect holder, and not a holder, of those debt securities.

Legal Holders. Our obligations, as well as the obligations of the trustee and those of any third parties employed by us or the trustee, run only to the legal holders of the debt securities. We do not have obligations to you if you hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether you choose to be an indirect holder of a debt security or have no choice because we are issuing the debt securities only in global form.

For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice, even if that holder is required, under agreements with depository participants or customers or by law, to pass it along to the indirect holders but does not do so. Similarly, if we want to obtain the approval of the holders for any purpose (for example, to amend the indenture or to relieve us of the consequences of a default or of our obligation to comply with a particular provision of the indenture) we would seek the approval only from the holders, and not the indirect holders, of the debt securities. Whether and how the holders contact the indirect holders is up to the holders.

When we refer to you, we mean those who invest in the debt securities being offered by this prospectus, whether they are the holders or only indirect holders of those debt securities. When we refer to your debt securities, we mean the debt securities in which you hold a direct or indirect interest.

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Special Considerations for Indirect Holders. If you hold debt securities through a bank, broker or other financial institution, either in book-entry form or in street name, you should check with your own institution to find out:

• how it handles securities payments and notices;

• whether it imposes fees or charges;

• how it would handle a request for the holders’ consent, if ever required;

• whether and how you can instruct it to send you debt securities registered in your own name so you can be a holder, if that is permitted in the future;

• how it would exercise rights under the debt securities if there were a default or other event triggering the need for holders to act to protect their interests; and

• if the debt securities are in book-entry form, how the depository’s rules and procedures will affect these matters.

Global Securities

What is a Global Security?We will issue each debt security under the indenture in book-entry form only, unless we specify otherwise in the applicable prospectus supplement. A global security represents one or any other number of individual debt securities. Generally, all debt securities represented by the same global securities will have the same terms. We may, however, issue a global security that represents multiple debt securities that have different terms and are issued at different times. We call this kind of global security a master global security.

Each debt security issued in book-entry form will be represented by a global security that we deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depository. Unless we specify otherwise in the applicable prospectus supplement, The Depository Trust Company, New York, New York, known as DTC, will be the depository for all debt securities issued in book-entry form.

A global security may not be transferred to or registered in the name of anyone other than the depository or its nominee, unless special termination situations arise. We describe those situations below under “Special Situations When a Global Security Will Be Terminated.” As a result of these arrangements, the depository, or its nominee, will be the sole registered owner and holder of all debt securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depository or with another institution that does. Thus, if your security is represented by a global security, you will not be a holder of the debt security, but only an indirect holder of a beneficial interest in the global security.

Special Considerations for Global Securities. We do not recognize an indirect holder as a holder of debt securities and instead deal only with the depository that holds the global security. The account rules of your financial institution and of the depository, as well as general laws relating to securities transfers, will govern your rights relating to a global security.

If we issue debt securities only in the form of a global security, you should be aware of the following:

• you cannot cause the debt securities to be registered in your name, and cannot obtainnon-global certificates for your interest in the debt securities, except in the special situations that we describe below;

• you will be an indirect holder and must look to your own bank or broker for payments on the debt securities and protection of your legal rights relating to the debt securities, as we describe under “Holders of Debt Securities” above;

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• you may not be able to sell interests in the debt securities to some insurance companies and to other institutions that are required by law to own their securities innon-book-entry form;

• you may not be able to pledge your interest in a global security in circumstances where certificates representing the debt securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;

• the depository’s policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to your interest in a global security. We and the trustee have no responsibility for any aspect of the depository’s actions or for its records of ownership interests in a global security. We and the trustee also do not supervise the depository in any way;

• DTC requires, and other depositories may require, that those who purchase and sell interests in a global security within its book-entry system use immediately available funds and your broker or bank may require you to do so as well; and

• financial institutions that participate in the depository’s book-entry system, and through which you hold your interest in a global security, may also have their own policies affecting payments, notices and other matters relating to the debt security. Your chain of ownership may contain more than one financial intermediary. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When a Global Security Will Be Terminated. In a few special situations described below, a global security will be terminated and interests in it will be exchanged for certificates innon-global form representing the debt securities it represented. After that exchange, you will be able to choose whether to hold the debt securities directly or in street name. You must consult your own bank or broker to find out how to have your interests in a global security transferred on termination to your own name, so that you will be a holder. We have described the rights of holders and street name investors above under “Holders of Debt Securities.”

The special situations for termination of a global security are as follows:

• if the depository notifies us that it is unwilling, unable or no longer qualified to continue as depository for that global security and we do not appoint another institution to act as depository within 60 days;

• if we notify the trustee that we wish to terminate that global security; or

• if an event of default has occurred with regard to debt securities represented by that global security and has not been cured or waived. We discuss defaults later under “Events of Default.”

If a global security is terminated, only the depository, and not we or the trustee, is responsible for deciding the names of the intermediary banks, brokers and other financial institutions in whose names the debt securities represented by the global security are registered, and, therefore, who will be the holders of those debt securities.

Covenants

This section summarizes the material covenants in the indenture. Please refer to the applicable prospectus supplement for information about any changes to our covenants, including any addition or deletion of a covenant, and to the indenture for information on other covenants not described in this prospectus or the applicable prospectus supplement.

Limitations on Liens. We covenant in the indenture that we will not, and will not permit any of our Restricted Subsidiaries to, create, incur, issue or assume any Indebtedness secured by any Lien on any Principal Property, or on shares of stock or Indebtedness of any Restricted Subsidiary, known as Restricted Securities, without making effective provision for the Outstanding Securities, other than debt securities of any series not entitled to the benefit of this covenant, to be secured by a Lien equally and ratably with, or prior to (or in the case

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of debt securities of any series that are subordinated in right of payment to the Indebtedness secured by such Lien, by a Lien subordinated to), the Lien securing such Indebtedness for so long as the Indebtedness is so secured, except that the foregoing restriction does not apply to:

• any Lien existing on the date of the first issuance of debt securities of the relevant series under the indenture, or existing on such other date as may be specified in any supplemental indenture, board resolution or officers’ certificate with respect to such series;

• any Lien on any Principal Property or Restricted Securities of any person existing at the time such person is merged or consolidated with or into us or a Restricted Subsidiary, or becomes a Restricted Subsidiary, or arising thereafter otherwise than in connection with the borrowing of money arranged thereafter and pursuant to contractual commitments entered into prior to and not in contemplation of such person’s becoming a Restricted Subsidiary;

• any Lien on any Principal Property or Restricted Securities existing at the time we or a Restricted Subsidiary acquire such Principal Property or Restricted Securities, whether or not such Lien is assumed by us or such Restricted Subsidiary, provided that no such Lien may extend to any other Principal Property or Restricted Securities of ours or any Restricted Subsidiary;

• any Lien on any Principal Property, including any improvements on an existing Principal Property, of ours or any Restricted Subsidiary, and any Lien on Restricted Securities of a Restricted Subsidiary that was formed or is held for the purpose of acquiring and holding such Principal Property, in each case to secure all or any part of the cost of acquisition, development, operation, construction, alteration, repair or improvement of all or any part of such Principal Property, or to secure Indebtedness incurred by us or a Restricted Subsidiary for the purpose of financing all or any part of such cost; provided that such Lien is created prior to, at the time of, or within 12 months after the latest of, the acquisition, completion of construction or improvement or commencement of commercial operation of that Principal Property and, provided further, that no such Lien may extend to any other Principal Property of ours or any Restricted Subsidiary, other than any currently unimproved real property on which the Principal Property has been constructed or developed or the improvement is located;

• any Lien on any Principal Property or Restricted Securities to secure Indebtedness owed to us or to a Restricted Subsidiary;

• any Lien in favor of a governmental body to secure advances or other payments under any contract or statute or to secure Indebtedness incurred to finance the purchase price or cost of constructing or improving the property subject to such Lien;

• any Lien created in connection with a project financed with, and created to secure,Non-Recourse Indebtedness;

• any extension, renewal, substitution or replacement, or successive extensions, renewals, substitutions or replacements, in whole or in part, of any Lien referred to in any of the bullet points above, provided that the Indebtedness secured thereby may not exceed the principal amount of Indebtedness that is secured at the time of the renewal or refunding, plus any premium, cost or expense in connection with such extensions, renewals, substitutions or replacements, and that such renewal or refunding Lien must be limited to all or any part of the same property and improvements, shares of stock or Indebtedness that secured the Lien that was renewed or refunded; or

• any Lien not permitted above securing Indebtedness that, together with the aggregate outstanding principal amount of other secured Indebtedness that would otherwise be subject to the above restrictions, excluding Indebtedness secured by Liens permitted under the above exceptions, and the Attributable Debt in respect of all Sale and Leaseback Transactions, not including Attributable Debt in respect of any such Sale and Leaseback Transactions described in the last two bullet points in the following paragraph, would not then exceed 15% of our Consolidated Net Tangible Assets.

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Limitation on Sale and Leaseback Transactions. We covenant in the indenture that we will not, and will not permit any Restricted Subsidiary to, enter into any Sale and Leaseback Transaction unless:

• we or a Restricted Subsidiary would be entitled, without securing the Outstanding Securities of any series, to incur Indebtedness secured by a Lien on the Principal Property that is the subject of such Sale and Leaseback Transaction pursuant to the provisions described in the preceding paragraph;

• the Attributable Debt associated with the Sale and Leaseback Transaction would be in an amount permitted under the last bullet point of the preceding paragraph;

• the proceeds received in respect of the Principal Property so sold and leased back at the time of entering into such Sale and Leaseback Transaction are to be used for our business and operations or the business and operations of any Subsidiary; or

• within 12 months after the sale or transfer, an amount equal to the proceeds received in respect of the Principal Property so sold and leased back at the time of entering into such Sale and Leaseback Transaction is applied to the prepayment, other than mandatory prepayment, of any Outstanding Securities or Funded Indebtedness that is owed by us or a Restricted Subsidiary, other than Funded Indebtedness that is held by us or any Restricted Subsidiary or our Funded Indebtedness that is subordinate in right of payment to any Outstanding Securities that are entitled to the benefit of this covenant.

Definitions. Following are definitions of some of the terms used in the covenants described above.

“Attributable Debt” means, as to any lease under which any person is at the time liable for rent, at any date as of which the amount thereof is to be determined, the total net amount of rent required to be paid by such person under such lease during the remaining term, excluding amounts required to be paid on account of maintenance and repairs, services, insurance, taxes, assessments, water rates and similar charges and contingent rents, discounted from the respective due dates thereof at the rate of interest (or Yield to Maturity, in the case of original issue discount securities) borne by the then Outstanding Securities, compounded monthly.

“Capital Stock” means any and all shares, interests, rights to purchase, warrants, options, participations or other equivalents of or interests, however designated, in stock issued by a corporation.

“Consolidated Net Tangible Assets” means the aggregate amount of assets, less applicable reserves and other properly deductible items, after deducting:

• all current liabilities, excluding any portion thereof constituting Funded Indebtedness; and

• all goodwill, trade names, trademarks, patents, unamortized debt discount and expense and other like intangibles,

all as set forth on our most recent consolidated balance sheet contained in our latest quarterly or annual report filed with the SEC under the Securities Exchange Act of 1934, as amended, and computed in accordance with generally accepted accounting principles.

“Funded Indebtedness” means, as applied to any person, all Indebtedness of such person maturing after, or renewable or extendible at the option of the person beyond, 12 months from the date of determination.

“Indebtedness” means obligations for money borrowed, evidenced by notes, bonds, debentures or other similar evidences of indebtedness.

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“Lien” means any lien, mortgage, pledge, encumbrance, charge or security interest securing Indebtedness; provided, however, that the following types of transactions will not be considered, for purposes of this definition, to result in a Lien:

• any acquisition by us or any Restricted Subsidiary of any property or assets subject to any reservation or exception under the terms of which any vendor, lessor or assignor creates, reserves or excepts or has created, reserved or excepted an interest in oil, gas or any other mineral in place or the proceeds thereof;

• any conveyance or assignment whereby we or any Restricted Subsidiary conveys or assigns to any person or persons an interest in oil, gas or any other mineral in place or the proceeds thereof;

• any Lien upon any property or assets either owned or leased by us or a Restricted Subsidiary or in which we or any Restricted Subsidiary owns an interest that secures for the benefit of the person or persons paying the expenses of developing or conducting operations for the recovery, storage, transportation or sale of the mineral resources of the property or assets, or property or assets with which it is unitized, the payment to such person or persons of our proportionate part or the Restricted Subsidiary’s proportionate part of such development or operating expenses;

• any lease classified as an operating lease under generally accepted accounting principles;

• any hedging arrangements entered into in the ordinary course of business, including any obligation to deliver any mineral, commodity or asset in connection therewith; or

• any guarantees that we make for the repayment of Indebtedness of any Subsidiary or guarantees by any Subsidiary of the repayment of Indebtedness of any entity.

“Non-Recourse Indebtedness” means, at any time, Indebtedness incurred after the date of the indenture by us or a Restricted Subsidiary in connection with the acquisition of property or assets by us or a Restricted Subsidiary or the financing of the construction of or improvements on property, whenever acquired, provided that, under the terms of this Indebtedness and under applicable law, the recourse at such time and thereafter of the lenders with respect to such Indebtedness is limited to the property or assets so acquired, or the construction or improvements, including Indebtedness as to which a performance or completion guarantee or similar undertaking was initially applicable to the Indebtedness or the related property or assets if the guarantee or similar undertaking has been satisfied and is no longer in effect. Indebtedness which is otherwiseNon-Recourse Indebtedness will not lose its character asNon-Recourse Indebtedness because there is recourse to us, any Subsidiary of ours or any other person for (a) environmental or tax warranties and indemnities and such other representations, warranties, covenants and indemnities as are customarily required in such transactions or (b) indemnities for and liabilities arising from fraud, misrepresentation, misapplication ornon-payment of rents, profits, insurance and condemnation proceeds and other sums actually received from secured assets to be paid to the lender, waste and mechanics’ liens or similar matters.

“Principal Property” means any natural gas distribution property located in the United States, except any property that in the opinion of our board of directors is not of material importance to the total business conducted by us and our consolidated Subsidiaries.

“Restricted Subsidiary” means any Subsidiary the amount of Consolidated Net Tangible Assets of which constitutes more than 10% of the aggregate amount of Consolidated Net Tangible Assets of us and our Subsidiaries.

“Sale and Leaseback Transaction” means any arrangement with any person in which we or any Restricted Subsidiary leases any Principal Property that has been or is to be sold or transferred by us or the Restricted Subsidiary to that person, other than any such arrangement involving:

• a lease for a term, including renewals at the option of the lessee, of not more than three years or classified as an operating lease under generally accepted accounting principles;

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• leases between us and a Restricted Subsidiary or between Restricted Subsidiaries; and

• leases of a Principal Property executed by the time of, or within 12 months after the latest of, the acquisition, the completion of construction or improvement, or the commencement of commercial operation, of the Principal Property, whichever is later.

“Subsidiary” of ours means:

• a corporation, a majority of whose Capital Stock with rights, under ordinary circumstances, to elect directors is owned, directly or indirectly, at the date of determination, by us, by one or more of our Subsidiaries or by us and one or more of our Subsidiaries; or

• any other person, other than a corporation, in which at the date of determination we, one or more of our Subsidiaries or we and one or more of our Subsidiaries, directly or indirectly, have at least a majority ownership and power to direct the policies, management and affairs of that person.

Consolidation, Merger or Sale of Assets. Under the terms of the indenture, we will be generally permitted to consolidate with or merge into another entity. We will also be permitted to sell or transfer our assets substantially as an entirety to another entity. However, we may not take any of these actions unless all of the following conditions are met:

• the resulting entity, or the person to which such assets will have been sold or transferred, must agree to be legally responsible for all our obligations relating to the debt securities and the indenture;

• the transaction must not cause a default or an Event of Default, or an event that with notice or lapse of time or both would become an Event of Default, as described below;

• the resulting entity, or the person to which such assets will have been sold or transferred, must be organized under the laws of the United States or one of the states or the District of Columbia; and

• we must deliver an officers’ certificate and legal opinion to the trustee with respect to the transaction.

In the event that we engage in one of these transactions and comply with the conditions listed above, we would be discharged from all our obligations and covenants under the indenture and all obligations under the Outstanding Securities, with the successor corporation or person succeeding to our obligations and covenants.

In the event that we engage in one of these transactions, the indenture provides that, if any Principal Property or Restricted Securities would thereupon become subject to any Lien securing Indebtedness, then the debt securities, other than debt securities not entitled to the benefits of specified covenants, must be secured, as to such Principal Property or Restricted Securities, equally and ratably with (or prior to or, in the case of debt securities that are subordinated in right of payment to the Indebtedness secured by such Lien or in the case of other Indebtedness of ours that is subordinated to the debt securities, on a subordinated basis to such Lien securing) the Indebtedness or obligations that upon the occurrence of such transaction would become secured by the Lien, unless the Lien could be created under the indenture without equally and ratably securing the debt securities (or, in the case of debt securities that are subordinated in right of payment to the Indebtedness secured by such Lien, on a subordinated basis to such Lien).

Modification or Waiver

There are two types of changes that we can make to the indenture and the debt securities.

Changes Requiring Approval. With the consent of the holders of at least a majority in principal amount of all outstanding debt securities of each series affected (including any such approvals obtained in connection with a tender or exchange offer for outstanding debt securities), we may make any changes, additions or deletions to any

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provisions of the indenture applicable to the affected series, or modify the rights of the holders of the debt securities of the affected series. However, without the consent of each holder affected, we cannot:

• change the stated maturity of the principal of, any premium on, or any installment of interest on any debt security;

• reduce the principal amount of, any premium on, or the rate of interest on any debt security;

• change any of our obligations to pay Additional Amounts;

• reduce the amount of the principal that would be due and payable upon a declaration of acceleration of maturity following the default of a debt security whose principal amount payable at stated maturity may be more or less than its principal face amount at original issuance or an original issue discount security;

• adversely affect any right of repayment at the holder’s option;

• change the place of payment of a debt security;

• impair the holder’s right to sue for payment;

• adversely affect any right to convert or exchange a debt security;

• reduce the percentage in principal amount of the outstanding debt securities of a series, the consent of whose holders is required to modify or amend the indenture; or

• modify certain provisions of the indenture dealing with suits for enforcement of payment by the trustee or modification and waiver, except to increase any percentage of consents required to amend the indenture or for any waiver, or to modify the provisions of the indenture dealing with the unconditional right of the holders of the debt securities to receive principal, premium, if any, and interest.

Changes Not Requiring Approval. The second type of change does not require the consent of any holders of the debt securities. This type is limited to clarifications and certain other changes that would not adversely affect holders of the outstanding debt securities in any material respect. Additionally, we do not need any approval to make any change that affects only debt securities to be issued under the indenture after the changes take effect.

Further Details Concerning Voting. When taking a vote, we will use the following rules to decide how much principal amount to attribute to a debt security:

• for original issue discount securities, we will use the principal amount that would be due and payable on the voting date if the maturity of the debt securities were accelerated to that date because of a default; and

• for debt securities whose principal amount is not known (for example, because it is based on an index) we will use a special rule for that debt security described in the applicable prospectus supplement.

Debt securities will not be considered outstanding, and therefore not eligible to vote, if we have deposited or set aside in trust money for their payment or redemption. Debt securities will also not be eligible to vote if they have been fully defeased as described later under “Defeasance and Covenant Defeasance.”

Book-entry and other indirect holders should consult their banks or brokers for information on how approval may be granted or denied if we seek to change the indenture or the debt securities or request a waiver.

Events of Default

Holders of debt securities will have special rights if an Event of Default occurs as to the debt securities of their series that is not cured, as described later in this subsection. Please refer to the applicable prospectus supplement for information about any changes to the Events of Default, including any addition of a provision providing event risk or similar protection.

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What is an Event of Default?The term “Event of Default” as to the debt securities of a series means any of the following:

• we do not pay interest on a debt security of the series within 30 days of its due date;

• we do not pay the principal of or any premium, if any, on a debt security of the series at its maturity;

• we do not deposit any sinking fund payment when and as due by the terms of any debt securities requiring such payment;

• we remain in breach of a covenant or agreement in the indenture, other than a covenant or agreement not for the benefit of the series, for 60 days after we receive written notice stating that we are in breach from the trustee or the holders of at least 25 percent of the principal amount of the debt securities of the series;

• we or a Restricted Subsidiary is in default under any matured or accelerated agreement or instrument under which we have outstanding Indebtedness for borrowed money or guarantees, which individually is in excess of $25,000,000, and we have not cured any acceleration within 30 days after we receive notice of this default from the trustee or the holders of at least 25 percent of the principal amount of the debt securities of the series, unless prior to the entry of judgment for the trustee, we or the Restricted Subsidiary remedy the default or the default is waived by the holders of the indebtedness;

• we file for bankruptcy or other events of bankruptcy, insolvency or reorganization occur; or

• any other Event of Default provided for the benefit of debt securities of the series.

An Event of Default for a particular series of debt securities will not necessarily constitute an Event of Default for any other series of debt securities issued under the indenture.

The trustee may withhold notice to the holders of debt securities of a particular series of any default if it considers its withholding of notice to be in the interest of the holders of that series, except that the trustee may not withhold notice of a default in the payment of the principal of, any premium on, or the interest on the debt securities or in the payment of any sinking fund installment with respect to the debt securities.

Remedies if an Event of Default Occurs. If an event of default has occurred and is continuing, the trustee or the holders of at least 25 percent in principal amount of the debt securities of the affected series may declare the entire principal amount and all accrued interest of all the debt securities of that series to be due and immediately payable by notifying us, and the trustee, if the holders give notice, in writing. This is called a declaration of acceleration of maturity.

If the maturity of any series of debt securities is accelerated and a judgment for payment has not yet been obtained, the holders of a majority in principal amount of the debt securities of that series may cancel the acceleration if all events of default other than thenon-payment of principal or interest on the debt securities of that series that have become due solely by a declaration of acceleration are cured or waived, and we deposit with the trustee a sufficient sum of money to pay:

• all overdue interest on outstanding debt securities of that series;

• all unpaid principal and any premium, if any, of any outstanding debt securities of that series that has become due otherwise than by a declaration of acceleration, and interest on the unpaid principal and any premium, if any;

• all interest on such overdue interest; and

• all amounts paid or advanced by the trustee for that series and reasonable compensation of the trustee.

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Except in cases of default, where the trustee has some special duties, the trustee is not required to take any action under the indenture at the request of any holders unless the holders offer the trustee reasonable protection from expenses and liability. This is called an indemnity. If reasonable indemnity is provided, the holders of a majority in principal amount of the outstanding debt securities of the relevant series may direct the time, method and place of conducting any lawsuit or other formal legal action seeking any remedy available to the trustee. The trustee may refuse to follow those directions if the directions conflict with any law or the indenture or expose the trustee to personal liability. No delay or omission in exercising any right or remedy will be treated as a waiver of that right, remedy or Event of Default.

Before a holder is allowed to bypass the trustee and bring his or her own lawsuit or other formal legal action or take other steps to enforce his or her rights or protect his or her interest relating to the debt securities, the following must occur:

• the holder must give the trustee written notice that an Event of Default has occurred and remains uncured;

• the holders of at least 25 percent in principal amount of all outstanding debt securities of the relevant series must make a written request that the trustee take action because of the default and must offer reasonable indemnity to the trustee against the cost and other liabilities of taking that action;

• the trustee must not have instituted a proceeding for 60 days after receipt of the above notice and offer of indemnity; and

• the holders of a majority in principal amount of the debt securities must not have given the trustee a direction inconsistent with the above notice during the60-day period.

However, a holder is entitled at any time to bring a lawsuit for the payment of money due on his or her debt securities on or after the due date without complying with the foregoing.

Holders of a majority in principal amount of the debt securities of the affected series may waive any past defaults other than the following:

• the payment of principal, any premium, or interest on any debt security; or

• in respect of a covenant that under the indenture cannot be modified or amended without the consent of each holder affected.

Each year, we will furnish the trustee with a written statement of two of our officers certifying that, to their knowledge, we are in compliance with the indenture and the debt securities, or else specifying any default.

Book-entry and other indirect holders should consult their banks or brokers for information on how to give notice or direction to or make a request of the trustee and how to declare or cancel an acceleration.

Defeasance and Covenant Defeasance

Unless we provide otherwise in the applicable prospectus supplement, the provisions for full defeasance and covenant defeasance described below apply to each series of debt securities. In general, we expect these provisions to apply to each debt security that is not a floating rate or indexed debt security.

Full Defeasance. If there is a change in U.S. federal tax law, as described below, we can legally release ourselves from all payment and other obligations on the debt securities, called “full defeasance,” if we put in place the following arrangements for you to be repaid:

• we must deposit in trust for the benefit of all holders of the debt securities a combination of money and obligations issued or guaranteed by the U.S. government that will generate enough cash to make interest, principal and any other payments on the debt securities on their various due dates; and

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• we must deliver to the trustee a legal opinion confirming that there has been a change in current federal tax law or an IRS ruling that lets us make the above deposit without causing you to be taxed on the debt securities any differently than if we did not make the deposit and just repaid the debt securities ourselves at maturity.

If we ever did accomplish defeasance, as described above, you would have to rely solely on the trust deposit for repayment of the debt securities. You could not look to us for repayment in the event of any shortfall. Conversely, the trust deposit would most likely be protected from claims of our lenders and other creditors if we ever become bankrupt or insolvent. If we accomplish a defeasance, we would retain only the obligations to register the transfer or exchange of the debt securities, to maintain an office or agency in respect of the debt securities and to hold moneys for payment in trust.

Covenant Defeasance. Under current federal tax law, we can make the same type of deposit described above and be released from any restrictive covenants in the indenture. This is called “covenant defeasance.” In that event, you would lose the protection of any such covenants but would gain the protection of having money and obligations issued or guaranteed by the U.S. government set aside in trust to repay the debt securities. In order to achieve covenant defeasance, we must do the following:

• deposit in trust for your benefit and the benefit of all other direct holders of the debt securities a combination of money and obligations issued or guaranteed by the U.S. government that will generate enough cash to make interest, principal and any other payments on the debt securities on their various due dates; and

• deliver to the trustee a legal opinion of our counsel confirming that, under current federal income tax law, we may make the deposit described above without causing you to be taxed on the debt securities any differently than if we did not make the deposit and just repaid the debt securities ourselves at maturity.

If we accomplish covenant defeasance, you can still look to us for repayment of the debt securities if there were a shortfall in the trust deposit or the trustee is prevented from making payment. In fact, if one of the remaining Events of Default occurred, such as our bankruptcy, and the debt securities became immediately due and payable, there may be a shortfall. Depending on the event causing the default, you may not be able to obtain payment of the shortfall.

Debt Securities Issued inNon-Global Form

If any debt securities cease to be issued in global form, they will be issued:

• only in fully registered form;

• without interest coupons; and

• unless we indicate otherwise in the prospectus supplement, in denominations of $2,000 and amounts that are integral multiples of $1,000 in excess thereof.

Holders may exchange their debt securities that are not in global form for debt securities of smaller denominations or combined into fewer debt securities of larger denominations, as long as the total principal amount is not changed.

Holders may exchange or transfer their debt securities at the office of the trustee. We may appoint the trustee to act as our agent for registering debt securities in the names of holders transferring debt securities, or we may appoint another entity to perform these functions or perform them ourselves.

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Holders will not be required to pay a service charge to transfer or exchange their debt securities, but they may be required to pay for any tax or other governmental charge associated with the transfer or exchange. The transfer or exchange will be made only if our transfer agent is satisfied with the holder’s proof of legal ownership.

If we have designated additional transfer agents for a holder’s debt security, they will be named in the applicable prospectus supplement. We may appoint additional transfer agents or cancel the appointment of any particular transfer agent. We may also approve a change in the office through which any transfer agent acts.

If any debt securities are redeemable and we redeem less than all those debt securities, we may stop the transfer or exchange of those debt securities during the period beginning 15 days before the day we mail the notice of redemption and ending on the day of that mailing, in order to freeze the list of holders to prepare the mailing. We may also refuse to register transfers or exchanges of any debt securities selected for redemption, except that we will continue to permit transfers and exchanges of the unredeemed portion of any debt security that will be partially redeemed.

If a debt security is issued as a global security, only the depository will be entitled to transfer and exchange the debt security as described in this section, since it will be the sole holder of the debt security.

Payment Mechanics

Who Receives Payment?If interest is due on a debt security on an interest payment date, we will pay the interest to the person or entity in whose name the debt security is registered at the close of business on the regular record date, discussed below, relating to the interest payment date. If interest is due at maturity but on a day that is not an interest payment date, we will pay the interest to the person or entity entitled to receive the principal of the debt security. If principal or another amount besides interest is due on a debt security at maturity, we will pay the amount to the holder of the debt security against surrender of the debt security at a proper place of payment, or, in the case of a global security, in accordance with the applicable policies of the depository.

Payments on Global Securities. We will make payments on a global security in accordance with the applicable policies of the depository as in effect from time to time. Under those policies, we will pay directly to the depository, or its nominee, and not to any indirect holders who own beneficial interests in the global security. An indirect holder’s right to those payments will be governed by the rules and practices of the depository and its participants, as described above under “What is a Global Security?”.

Payments onNon-Global Securities. For a debt security innon-global form, we will pay interest that is due on an interest payment date by check mailed on the interest payment date to the holder at his or her address shown on the trustee’s records as of the close of business on the regular record date. We will make all other payments by check, at the paying agent described below, against surrender of the debt security. We will make all payments by check innext-day funds; for example, funds that become available on the day after the check is cashed.

Alternatively, if anon-global security has a face amount of at least $1,000,000 and the holder asks us to do so, we will pay any amount that becomes due on the debt security by wire transfer of immediately available funds to an account at a bank in New York City on the due date. To request wire payment, the holder must give the paying agent appropriate transfer instructions at least five business days before the requested wire payment is due. In the case of any interest payment due on an interest payment date, the instructions must be given by the person who is the holder on the relevant regular record date. In the case of any other payment, we will make payment only after the debt security is surrendered to the paying agent. Any wire instructions, once properly given, will remain in effect unless and until new instructions are given in the manner described above.

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Regular Record Dates. We will pay interest to the holders listed in the trustee’s records as the owners of the debt securities at the close of business on a particular day in advance of each interest payment date. We will pay interest to these holders if they are listed as the owner even if they no longer own the debt security on the interest payment date. That particular day, usually about two weeks in advance of the interest payment date, is called the “regular record date” and will be identified in the prospectus supplement.

Payment When Offices Are Closed. If any payment is due on a debt security on a day that is not a business day, we will make the payment on the next business day. Payments postponed to the next business day in this situation will be treated under the indenture as if they were made on the original due date. A postponement of this kind will not result in a default under any debt security or the indenture, and no interest will accrue on the postponed amount from the original due date to the next business day.

Paying Agents. We may appoint one or more financial institutions to act as our paying agents, at whose designated offices debt securities innon-global form may be surrendered for payment at their maturity. We call each of those offices a paying agent. We may add, replace or terminate paying agents from time to time. We may also choose to act as our own paying agent. Initially, we have appointed the trustee, at its corporate trust office in New York City, as the paying agent. We must notify you of changes in the paying agents.

Book-entry and other indirect holders should consult their banks or brokers for information on how they will receive payments on their debt securities.

The Trustee Under the Indenture

U.S. Bank National Association is the trustee under the indenture for our debt securities. We will identify any other entity acting as the trustee for a series of debt securities that we may offer in the prospectus supplement for the offering of such debt securities.

The trustee may resign or be removed with respect to one or more series of debt securities and a successor trustee may be appointed to act with respect to these series.

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DESCRIPTION OF COMMON STOCK

The following summary of our common stock, no par value per share (the “common stock”), is based on and qualified by reference to, our Restated Articles of Incorporation filed in Texas and Virginia (the “Articles of Incorporation”) and Amended and Restated Bylaws (the “Bylaws”). For a complete description of the terms and provisions of our equity securities, including our common stock, refer to the Articles of Incorporation and Bylaws, each of which are filed as exhibits to our annual reports on Form10-K filed with the SEC. See “Where You Can Find More Information.”

General

Our authorized capital stock consists of 200,000,000 shares of common stock, no par value, of which 122,267,437 shares were outstanding on February 10, 2020. Each of our shares of common stock is entitled to one vote on all matters voted upon by shareholders. Our shareholders do not have cumulative voting rights. With respect to any matter, other than a matter for which the affirmative vote of the holders of a specified portion of common stock may be required by law or our Articles of Incorporation, an act of the shareholders requires the affirmative vote of the holders of a majority of the shares entitled to vote on a matter and represented in person or by proxy at a meeting at which a quorum is present. The power to alter, amend or repeal the Bylaws, and to adopt new Bylaws, is vested in our Board of Directors, subject to repeal or change by the affirmative vote of the holders of 75 percent of the outstanding shares of common stock entitled to vote thereon.

Our issued and outstanding shares of common stock are fully paid and nonassessable. There are no redemption or sinking fund provisions applicable to the shares of our common stock, and such shares are not entitled to any preemptive rights. Since we are incorporated in both Texas and Virginia, we must comply with the laws of both states when issuing shares of our common stock.

Holders of our shares of common stock are entitled to receive such dividends as may be declared from time to time by our board of directors from our assets legally available for the payment of dividends and, upon our liquidation, a pro rata share of all of our assets available for distribution to our shareholders.

American Stock Transfer & Trust Company is the registrar and transfer agent for our common stock. Our common stock is listed on the New York Stock Exchange under the trading symbol “ATO.”

Charter and Bylaws Provisions

Some provisions of our Articles of Incorporation and Bylaws may be deemed to have an “anti-takeover” effect. The following description of these provisions is only a summary, and we refer you to our Articles of Incorporation and Bylaws for more information.

Cumulative Voting. Our Articles of Incorporation prohibit cumulative voting. In general, in the absence of cumulative voting, one or more persons who hold a majority of our outstanding shares can elect all of the directors who are subject to election at any meeting of shareholders.

Removal of Directors. Our Articles of Incorporation and Bylaws also provide that our directors may be removed only for cause and upon the affirmative vote of the holders of at least 75 percent of the shares then entitled to vote at an election of directors.

Fair Price Provisions. Article VII of our Articles of Incorporation provides certain “Fair Price Provisions” for our shareholders. Under Article VII, a merger, consolidation, sale of assets, share exchange, recapitalization or other similar transaction, between us or a company controlled by or under common control with us and any individual, corporation or other entity which, alone or together with its affiliates or associates, owns or controls 10 percent or more of our voting capital stock, would be required to satisfy the condition that the aggregate

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consideration per share to be received in the transaction for each class of our voting capital stock be at least equal to the highest per share price, or equivalent price for any different classes or series of stock, paid by the 10 percent shareholder in acquiring any of its holdings of our stock. If a proposed transaction with a 10 percent shareholder does not meet this condition, then the transaction must be approved by the holders of at least 75 percent of the outstanding shares of voting capital stock held by our shareholders other than the 10 percent shareholder, unless a majority of the directors who were members of our board immediately prior to the time the 10 percent shareholder involved in the proposed transaction became a 10 percent shareholder have either:

• expressly approved in advance the acquisition of the outstanding shares of our voting capital stock that caused the 10 percent shareholder to become a 10 percent shareholder; or

• approved the transaction either in advance of or subsequent to the 10 percent shareholder becoming a 10 percent shareholder.

The provisions of Article VII may not be amended, altered, changed, or repealed except by the affirmative vote of at least 75 percent of the votes entitled to be cast thereon at a meeting of our shareholders duly called for consideration of such amendment, alteration, change, or repeal. In addition, if there is a 10 percent shareholder, such action must also be approved by the affirmative vote of at least 75 percent of the outstanding shares of our voting capital stock held by the shareholders other than the 10 percent shareholder.

Shareholder Proposals and Director Nominations. Our shareholders can submit shareholder proposals and nominate candidates for the board of directors if the shareholders follow the advance notice procedures described in our Bylaws.

Shareholder proposals (other than those sought to be included in our proxy statement) must be submitted to our corporate secretary at least 60 days, but not more than 85 days, before the annual meeting; provided, however, that if less than 75 days’ notice or prior public disclosure of the date of the annual meeting is given or made to shareholders, notice by the shareholder to be timely must be received by our corporate secretary no later than the close of business on the 25th day following the day on which such notice of the date of the annual meeting was provided or such public disclosure was made. The notice must include a description of the proposal, the shareholder’s name and address and the number of shares held, and all other information which would be required to be included in a proxy statement filed with the SEC if the shareholder were a participant in a solicitation subject to the SEC’s proxy rules. To be included in our proxy statement for an annual meeting, our corporate secretary must receive the proposal at least 120 days prior to the anniversary of the date we mailed the proxy statement for the prior year’s annual meeting.

To nominate directors, shareholders must submit a written notice to our corporate secretary at least 60 days, but not more than 85 days, before a scheduled meeting; provided, however, that if less than 75 days’ notice or prior public disclosure of the date of the annual meeting is given or made to shareholders, such nomination shall have been received by our corporate secretary no later than the close of business on the 25th day following the day on which such notice of the date of the annual meeting was mailed or such public disclosure was made. The notice must include the name and address of the shareholder and of the shareholder’s nominee, the number of shares held by the shareholder, a representation that the shareholder is a holder of record of common stock entitled to vote at the meeting, and that the shareholder intends to appear in person or by proxy to nominate the persons specified in the notice, a description of any arrangements between the shareholder and the shareholder’s nominee, information about the shareholder’s nominee required by the SEC and the written consent of the shareholder’s nominee to serve as a director.

Shareholder proposals and director nominations that are late or that do not include all required information may be rejected. This could prevent shareholders from bringing certain matters before an annual or special meeting or making nominations for directors.

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PLAN OF DISTRIBUTION

We may sell the securities offered by this prospectus and a prospectus supplement as follows:

• through agents;

• to or through underwriters;

• through dealers;

• directly by us to purchasers;

• in “at the market offerings,” within the meaning of Rule 415(a)(4) of the Securities Act; or

• through a combination of any such methods of sale.

We, directly or through agents or dealers, may sell, and the underwriters may resell, the securities in one or more transactions, including:

• transactions on the New York Stock Exchange or any other organized market where the securities may be traded;

• in theover-the-counter market;

• in negotiated transactions; or

• through a combination of any such methods of sale.

The securities may be sold at a fixed price or prices which may be changed, at market prices prevailing at the time of sale, at prices related to such prevailing market prices or at negotiated prices.

We may designate underwriters or agents to solicit purchases of shares of our common stock for the period of their appointment and to sell securities on a continuing basis, including pursuant to“at-the-market offerings.” We will do so pursuant to the terms of a distribution agreement between us and the underwriters or agents. If we engage inat-the-market sales pursuant to a distribution agreement, we will issue and sell the shares to or through one or more underwriters or agents, which may act on an agency basis or on a principal basis. During the term of any such distribution agreement, we may sell shares on a daily basis in exchange transactions or otherwise as we agree with the underwriters or agents. The distribution agreement may provide that any shares of our common stock sold will be sold at prices related to the then prevailing market prices for our securities. Therefore, exact figures regarding net proceeds to us or commissions to be paid are impossible to determine and will be described in a prospectus supplement. The terms of each such distribution agreement will be set forth in more detail in a prospectus supplement to this prospectus. To the extent that any named underwriter or agent acts as principal pursuant to the terms of a distribution agreement, or if we offer to sell shares of our common stock through another broker dealer acting as underwriter, then such named underwriter may engage in certain transactions that stabilize, maintain or otherwise affect the price of our shares. We will describe any such activities in the prospectus supplement relating to the transaction. To the extent that any named broker dealer or agent acts as agent on a best efforts basis pursuant to the terms of a distribution agreement, such broker dealer or agent will not engage in any such stabilization transactions.

Agents designated by us from time to time may solicit offers to purchase the securities. We will name any such agent involved in the offer or sale of the securities and set forth any commissions payable by us to such agent in a prospectus supplement relating to any such offer and sale of securities. Unless otherwise indicated in the prospectus supplement, any such agent will be acting on a best efforts basis for the period of its appointment. Any such agent may be deemed to be an underwriter of the securities, as that term is defined in the Securities Act.

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If underwriters are used in the sale of securities, securities will be acquired by the underwriters for their own account and may be resold from time to time in one or more transactions. Securities may be offered to the public either through underwriting syndicates represented by one or more managing underwriters or directly by one or more firms acting as underwriters. If an underwriter or underwriters are used in the sale of securities, we will execute an underwriting agreement with such underwriter or underwriters at the time an agreement for such sale is reached. We will set forth in the prospectus supplement the names of the specific managing underwriter or underwriters, as well as any other underwriters, and the terms of the transactions, including compensation of the underwriters and dealers. Such compensation may be in the form of discounts, concessions or commissions. Underwriters and others participating in any offering of securities may engage in transactions that stabilize, maintain or otherwise affect the price of such securities. We will describe any such activities in the prospectus supplement.

We may elect to list any class or series of securities on any exchange, but we are not currently obligated to do so. It is possible that one or more underwriters, if any, may make a market in a class or series of securities, but the underwriters will not be obligated to do so and may discontinue any market making at any time without notice. We cannot give any assurance as to the liquidity of the trading market for any of the securities we may offer.

If a dealer is used in the sale of the securities, we or an underwriter will sell such securities to the dealer, as principal. The dealer may then resell such securities to the public at varying prices to be determined by such dealer at the time of resale. The prospectus supplement will set forth the name of the dealer and the terms of the transactions.

We may directly solicit offers to purchase the securities, and we may sell directly to institutional investors or others. These persons may be deemed to be underwriters within the meaning of the Securities Act with respect to any resale of the securities. The prospectus supplement will describe the terms of any such sales, including the terms of any bidding, auction or other process, if used.

Agents, underwriters and dealers may be entitled under agreements which may be entered into with us to indemnification by us against specified liabilities, including liabilities under the Securities Act, or to contribution by us to payments they may be required to make in respect of such liabilities. The prospectus supplement will describe the terms and conditions of such indemnification or contribution. Some of the agents, underwriters or dealers, or their affiliates, may engage in transactions with or perform services for us and our subsidiaries in the ordinary course of their business.

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LEGAL MATTERS

Gibson, Dunn & Crutcher LLP and Hunton Andrews Kurth LLP, Richmond, Virginia, have each rendered an opinion with respect to the validity of the securities that may be offered under this prospectus. We filed these opinions as exhibits to the registration statement of which this prospectus is a part. If counsel for any underwriters passes on legal matters in connection with an offering made under this prospectus, we will name that counsel in the prospectus supplement relating to that offering.

EXPERTS

The consolidated financial statements of Atmos Energy appearing in Atmos Energy’s Annual Report (Form10-K) for the fiscal year ended September 30, 2019 (including the schedule appearing therein), and the effectiveness of Atmos Energy’s internal control over financial reporting as of September 30, 2019 have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

With respect to the unaudited condensed consolidated interim financial information of Atmos Energy for the three-month periods ended December 31, 2019 and December 31, 2018, incorporated by reference in this Prospectus, Ernst & Young LLP reported that they have applied limited procedures in accordance with professional standards for a review of such information. However, their separate report dated February 4, 2020, included in Atmos Energy’s Quarterly Report on Form 10-Q for the quarter ended December 31, 2019, and incorporated by reference herein, states that they did not audit and they do not express an opinion on that interim financial information. Accordingly, the degree of reliance on their report on such information should be restricted in light of the limited nature of the review procedures applied. Ernst & Young LLP is not subject to the liability provisions of Section 11 of the Securities Act of 1933 (the “Act”) for their report on the unaudited interim financial information because that report is not a “report” or a “part” of the Registration Statement prepared or certified by Ernst & Young LLP within the meaning of Sections 7 and 11 of the Act.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission under the Securities Exchange Act of 1934, as amended (the “Exchange Act”).

The SEC maintains a website that contains reports, proxy statements and other information about issuers, like us, who file electronically with the SEC. The address of that site iswww.sec.gov. Unless specifically listed below under “Incorporation of Certain Documents by Reference” the information contained on the SEC website is not incorporated by reference into this prospectus.

You can also inspect reports, proxy statements and other information about us at the offices of the New York Stock Exchange, Inc., 11 Wall Street, New York, New York 10005.

We have filed with the SEC a registration statement on FormS-3, of which this prospectus is a part, which registers the securities we are offering. The registration statement, including the attached exhibits and schedules, contains additional relevant information about us and the securities offered. The rules and regulations of the SEC allow us to omit certain information included in the registration statement from this prospectus.

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INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” information in this prospectus that we have filed with it. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be part of this prospectus, except for any information that is superseded by information that is included directly in this prospectus or the applicable prospectus supplement relating to an offering of our securities.

We incorporate by reference into this prospectus the documents listed below and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of our offering of securities. These additional documents include periodic reports, such as annual reports on Form10-K and quarterly reports on Form10-Q, and current reports on Form8-K (other than information furnished under Items 2.02 and 7.01 or corresponding information furnished under Item 9.01 as an exhibit, which is deemed not to be incorporated by reference in this prospectus), as well as proxy statements (other than information identified in them as not incorporated by reference). You should review these filings as they may disclose a change in our business, prospects, financial condition or other affairs after the date of this prospectus.

This prospectus incorporates by reference the documents listed below that we have filed with the SEC but have not been included or delivered with this document:

• Our annual report onForm10-K for the year ended September 30, 2019;

• The following pages and captioned text contained in ourdefinitive proxy statement for the annual meeting of shareholders on February 5, 2020 and incorporated into our annual report on Form10-K: pages 7 through 14 under the captions“Corporate Governance and Other Board Matters — Independence of Directors”“— Committees of the Board of Directors”and“— Related Party Transactions and Review Policy;” pages 18 through 24 under the caption“Proposal One — Election of Directors — Nominees for Director;” pages 25 through 27 under the caption“Director Compensation;” pages 28 through 29 under the captions“Proposal Two — Ratification of Appointment of Independent Registered Public Accounting Firm — Audit and Related Fees” and “— Audit CommitteePre-Approval Policy;”pages 31 through 42 under the caption“Compensation Discussion and Analysis;” pages 43 through 56 under the caption“Named Executive Officer Compensation;”pages 57 through 58 under the caption“Other Executive Compensation Matters;” and pages 59 through 60 under the caption“Beneficial Ownership of Common Stock”;

• Our quarterly report onForm10-Q for the quarter ended December 31, 2019; and

• Our current reports onForm8-K filed onOctober  2, 2019 (two filed on this date) andFebruary 10, 2020.

These documents contain important information about us and our financial condition.

You may obtain a copy of any of these filings, or any of our future filings, from us without charge by requesting it in writing or by telephone at the following address or telephone number:

Atmos Energy Corporation

1800 Three Lincoln Centre

5430 LBJ Freeway

Dallas, Texas 75240

Attention: Jennifer Hills

(972)934-9227

Our website iswww.atmosenergy.com;any information on or connected to our website is not part of this prospectus.

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Atmos Energy Corporation

Common Stock

Having an Aggregate Offering Price of up to $1,000,000,000

PROSPECTUS SUPPLEMENT

Morgan Stanley	BofA Securities	BNP PARIBAS	CIBC Capital Markets
Credit Agricole CIB	Goldman Sachs & Co. LLC	J.P. Morgan	Mizuho Securities
MUFG	SunTrust Robinson Humphrey	TD Securities	Wells Fargo Securities

February 12, 2020