Korea Development Bank 424B2 Prospectus for primary offering

Filed Pursuant to Rule 424(b)(2)
Registration No. 333-217914

PROSPECTUS SUPPLEMENT

(To Prospectus Dated June 20, 2017)

The Korea Development Bank

US$500,000,000 Floating Rate Notes due 2020

US$150,000,000 Floating Rate Notes due 2022

US$350,000,000 2.750% Notes due 2023

Our US$500,000,000 aggregate principal amount of floating rate notes due 2020 (the “2020 Notes”) will bear interest at a rate equal to Three-Month USD LIBOR (as defined herein) plus 0.675% per annum. Interest on the 2020 Notes is payable quarterly in arrears on March 19, June 19, September 19 and December 19 of each year. The first interest payment on the 2020 Notes will be made on December 19, 2017 in respect of the period from (and including) September 19, 2017 to (but excluding) December 19, 2017. The 2020 Notes will mature on September 19, 2020.

Our US$150,000,000 aggregate principal amount of floating rate notes due 2022 (the “2022 Notes”, and together with the 2020 Notes, the “Floating Rate Notes”) will bear interest at a rate equal to Three-Month USD LIBOR (as defined herein) plus 0.705% per annum. Interest on the 2022 Notes is payable quarterly in arrears on February 27, May 27, August 27 and November 27 of each year. The first interest payment on the 2022 Notes will be made on November 27, 2017 in respect of the period from (and including) August 27, 2017 to (but excluding) November 27, 2017. The 2022 Notes will mature on February 27, 2022. The 2022 Notes offered hereby shall constitute a further issuance of, and be fungible with and be consolidated and form a single series with, our US$500,000,000 floating rate notes due 2022 issued on February 27, 2017 (the “Original 2022 Notes”). The total principal amount of the Original 2022 Notes and the 2022 Notes now being issued will be US$650,000,000.

Our US$350,000,000 aggregate principal amount of notes due 2023 (the “Fixed Rate Notes”) will bear interest at a rate of 2.750% per annum. Interest on the Fixed Rate Notes is payablesemi-annually in arrears on March 19 and September 19 of each year, beginning on March 19, 2018. The Fixed Rate Notes will mature on March 19, 2023.

All references to the “Notes” are to the 2020 Notes, the 2022 Notes and the Fixed Rate Notes, collectively.

The Notes will be issued in minimum denominations of US$200,000 principal amount and integral multiples of US$1,000 in excess thereof. The Notes will be represented by one or more global notes registered in the name of a nominee of The Depository Trust Company, as depositary.

The payment of interest and the repayment of principal on the Notes will not be guaranteed by the Government (as defined herein).

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

	2020 Notes					2022 Notes					Fixed Rate Notes
	Per Note			Total		Per Note			Total		Per Note			Total
Public offering price		100.000	%	US$	500,000,000		99.599	%	US$	149,398,500		99.975	%	US$	349,912,500
Underwriting discount		0.300	%	US$	1,500,000		0.300	%	US$	450,000		0.300	%	US$	1,050,000
Proceeds to us (before deduction of expenses)		99.700	%	US$	498,500,000		99.299	%	US$	148,948,500		99.675	%	US$	348,862,500

For the 2020 Notes and the Fixed Rate Notes, in addition to the initial public offering price, you will have to pay for accrued interest, if any, from and including September 19, 2017.

For the 2022 Notes, in addition to the initial public offering price, you will have to pay for accrued interest from and including August 27, 2017 to but excluding September 19, 2017.

Applications will be made to the Singapore Exchange Securities Trading Limited (the “SGX-ST”) for the listing and quotation of the Notes. The SGX-ST assumes no responsibility for the correctness of any statements made, opinions expressed or reports contained in this prospectus supplement and the accompanying prospectus. Approval in-principle from, admission to the Official List of, and the listing and quotation of any Notes on, the SGX-ST are not to be taken as an indication of the merits of the issuer or the Notes. Currently, there is no public market for the Notes.

We expect to make delivery of the Notes to investors through the book-entry facilities of The Depository Trust Company on or about September 19, 2017.

Joint Bookrunners and Lead Managers

Goldman Sachs International
	KDB Asia
		Mirae Asset Daewoo
			Mizuho Securities
				Morgan Stanley
					Société Générale Corporate & Investment Banking
						UBS

Prospectus Supplement Dated September 12, 2017

You should rely only on the information contained in or incorporated by reference in this prospectus supplement and the accompanying prospectus. We have not authorized anyone to provide you with different information. We are not making an offer to sell these securities in any state or jurisdiction where the offer or sale is not permitted.

TABLE OF CONTENTS

Prospectus Supplement

	Page
Summary of the Offering		S-5
Use of Proceeds		S-7
Recent Developments		S-8
Description of the Notes		S-14
Clearance and Settlement		S-18
Taxation		S-21
Underwriting		S-22
Legal Matters		S-28
Official Statements and Documents		S-28
General Information		S-28

Prospectus

	Page
Certain Defined Terms and Conventions		1
Use of Proceeds		2
The Korea Development Bank		3
Overview		3
Capitalization		7
Business		7
Selected Financial Statement Data		9
Operations		16
Sources of Funds		23
Debt		24
Overseas Operations		26
Property		26
Directors and Management; Employees		26
Tables and Supplementary Information		27
Financial Statements and the Auditors		32
The Republic of Korea		157
Land and History		157
Government and Politics		159
The Economy		162
Principal Sectors of the Economy		170
The Financial System		177
Monetary Policy		182
Balance of Payments and Foreign Trade		186
Government Finance		194
Debt		197
Tables and Supplementary Information		199

S-1

	Page
Description of the Securities		202
Description of Debt Securities		202
Description of Warrants		208
Terms Applicable to Debt Securities and Warrants		209
Description of Guarantees to be Issued by Us		210
Description of Guarantees to be Issued by The Republic of Korea		210
Limitations on Issuance of Bearer Debt Securities and Bearer Warrants		212
Taxation		213
Korean Taxation		213
United States Tax Considerations		215
Plan of Distribution		223
Legal Matters		224
Authorized Representatives in the United States		224
Official Statements and Documents		224
Experts		224
Forward-Looking Statements		225
Further Information		227

S-2

Certain Defined Terms

All references to “we” or “us” mean The Korea Development Bank. All references to “Korea” or the “Republic” contained in this prospectus supplement mean The Republic of Korea. All references to the “Government” mean the government of Korea. Terms used but not defined in this prospectus supplement shall have the same meanings given to them in the accompanying prospectus.

Our separate financial information as of and for the six months ended June 30, 2016 and 2017 included in this prospectus supplement has been prepared in accordance with International Financial Reporting Standards as adopted in Korea (“Korean IFRS” or “K-IFRS”). References in this prospectus supplement to “separate” financial statements and information are to financial statements and information prepared on a non-consolidated basis. Unless specified otherwise, our financial and other information included in this prospectus supplement is presented on a separate basis in accordance with Korean IFRS and does not include such information with respect to our subsidiaries.

In this prospectus supplement and the accompanying prospectus, where information has been provided in units of thousands, millions or billions, such amounts have been rounded up or down. Accordingly, actual numbers may differ from those contained herein due to rounding. Any discrepancy between the stated total amount and the actual sum of the itemized amounts listed in a table, is due to rounding.

Additional Information

The information in this prospectus supplement is in addition to the information contained in our prospectus dated June 20, 2017. The accompanying prospectus contains information regarding ourselves and Korea, as well as a description of some terms of the Notes. You can find further information regarding us, Korea, and the Notes in registration statement no.333-217914, as amended, relating to our debt securities, with or without warrants, and guarantees, which is on file with the U.S. Securities and Exchange Commission.

We are Responsible for the Accuracy of the Information in this Document

We are responsible for the accuracy of the information in this document and confirm that to the best of our knowledge we have included all facts that should be included not to mislead potential investors. TheSGX-ST assumes no responsibility for the correctness of any statements made, opinions expressed or reports contained in this prospectus supplement and the accompanying prospectus. Approval in-principle from, admission to the Official List of, and the listing and quotation of the Notes on, theSGX-ST are not to be taken as an indication of the merits of the issuer or the Notes.

Not an Offer if Prohibited by Law

The distribution of this prospectus supplement and the accompanying prospectus, and the offer of the Notes, may be legally restricted in some countries. If you wish to distribute this prospectus supplement or the accompanying prospectus, you should observe any restrictions. This prospectus supplement and the accompanying prospectus should not be considered an offer and should not be used to make an offer, in any state or country which prohibits the offering.

The Notes may not be offered or sold in Korea, directly or indirectly, or to any resident of Korea, except as permitted by Korean law. For more information, see “Underwriting—Foreign Selling Restrictions.”

S-3

Information Presented Accurate as of Date of Document

This prospectus supplement and the accompanying prospectus are the only documents on which you should rely for information about the offering. We have authorized no one to provide you with different information. You should not assume that the information in this prospectus supplement or the accompanying prospectus is accurate as of any date other than the date on the front of each document.

S-4

SUMMARY OF THE OFFERING

This summary highlights selected information from this prospectus supplement and the accompanying prospectus and may not contain all of the information that is important to you. To understand the terms of our Notes, you should carefully read this prospectus supplement and the accompanying prospectus.

The Notes

We are offering US$500,000,000 aggregate principal amount of floating rate notes due September 19, 2020 (the “2020 Notes”), US$150,000,000 aggregate principal amount of floating rate notes due February 27, 2022 (the “2022 Notes”, and together with the 2020 Notes, the “Floating Rate Notes”) and US$350,000,000 aggregate principal amount of 2.750% notes due March 19, 2023 (the “Fixed Rate Notes”). The 2022 Notes offered hereby shall constitute a further issuance of, and be fungible with and be consolidated and form a single series with, our US$500,000,000 floating rate notes due 2022 issued on February 27, 2017 (the “Original 2022 Notes”). The total principal amount of the Original 2022 Notes and the 2022 Notes now being issued will be US$650,000,000. All references to the “Notes” are to the 2020 Notes, the 2022 Notes and the Fixed Rate Notes, collectively.

The Notes will be issued in minimum denominations of US$200,000 principal amount and integral multiples of US$1,000 in excess thereof. The Notes will be represented by one or more global securities registered in the name of a nominee of The Depository Trust Company (“DTC”), as depositary.

The payment of interest and the repayment of principal on the Notes will not be guaranteed by the Government.

We do not have any right to redeem the Notes prior to maturity.

Floating Rate Notes

The 2020 Notes will bear interest at a rate equal to Three-Month USD LIBOR plus 0.675% per annum, payable quarterly in arrears on March 19, June 19, September 19 and December 19 of each year. The first interest payment on the 2020 Notes will be made on December 19, 2017, in respect of the period from (and including) September 19, 2017 to (but excluding) December 19, 2017. Interest on the 2020 Notes will accrue from September 19, 2017, and will be computed on the basis of the actual number of days in the applicable Interest Period divided by 360.

The 2022 Notes will bear interest at a rate equal to Three-Month USD LIBOR plus 0.705% per annum, payable quarterly in arrears on February 27, May 27, August 27 and November 27 of each year. The first interest payment on the 2022 Notes will be made on November 27, 2017 in respect of the period from (and including) August 27, 2017 to (but excluding) November 27, 2017. Interest on the 2022 Notes will accrue from August 27, 2017, and will be computed on the basis of the actual number of days in the applicable Interest Period divided by 360.

Fixed Rate Notes

The Fixed Rate Notes will bear interest at a rate of 2.750% per annum, payable semi-annually in arrears on March 19 and September 19, beginning on March 19, 2018. Interest on the Fixed Rate Notes will accrue from September 19, 2017 and will be computed based on a 360-day year consisting of twelve 30-day months.

See “Description of the Notes—Payment of Principal and Interest.”

S-5

Listing

Applications will be made to the SGX-ST for the listing and quotation of the Notes. Settlement of the Notes is not conditioned on obtaining the listing. For so long as the Notes are listed on the SGX-ST and the rules of the SGX-ST so require, the Notes will be traded on the SGX-ST in a minimum board lot size of US$200,000 or its equivalent in foreign currencies.

Form and Settlement

We will issue each series of the Notes in the form of one or more fully registered global notes, registered in the name of a nominee of DTC, as depositary. Except as described in the accompanying prospectus under “Description of the Securities—Description of Debt Securities—Global Securities,” the global notes will not be exchangeable for Notes in definitive registered form, and will not be issued in definitive registered form. Financial institutions, acting as direct and indirect participants in DTC, will represent your beneficial interests in the global notes. These financial institutions will record the ownership and transfer of your beneficial interest through book-entry accounts. You may hold your beneficial interests in the Notes through Euroclear Bank S.A./N.V. (“Euroclear”) or Clearstream Banking,société anonyme(“Clearstream”) if you are a participant in such systems, or indirectly through organizations that are participants in such systems. Any secondary market trading of book-entry interests in the Notes will take place through DTC participants, including Euroclear and Clearstream. See “Clearance and Settlement—Transfers Within and Between DTC, Euroclear and Clearstream.”

Further Issues

We may from time to time, without the consent of the holders of the Notes, create and issue additional debt securities with the same terms and conditions as either series of the Notes in all respects so that such further issue shall be consolidated and form a single series with the relevant series of the Notes. We will not issue any such additional debt securities unless such additional securities have no more than ade minimis amount of original issue discount or such issuance would otherwise constitute a “qualified reopening” for U.S. federal income tax purposes.

Delivery of the Notes

We expect to make delivery of the Notes, against payment insame-day funds on or about September 19, 2017, which we expect will be the fifth business day following the date of this prospectus supplement, referred to as “T+5.” You should note that initial trading of the Notes may be affected by the T+5 settlement. See “Underwriting—Delivery of the Notes.”

Underwriting

KDB Asia Limited, one of the underwriters, is our affiliate and has agreed to offer and sell the Notes only outside the United States to non-U.S. persons. See “Underwriting—Relationship with the Underwriters.”

S-6

USE OF PROCEEDS

The net proceeds from the issue of the Notes, after deducting the underwriting discount but not estimated expenses, will be US$996,311,000. We will use the net proceeds from the sale of the Notes for our general operations, including extending foreign currency loans and repayment of our maturing debt and other obligations.

S-7

RECENT DEVELOPMENTS

This section provides information that supplements the information about our bank and the Republic included under the headings corresponding to the headings below in the accompanying prospectus dated June 20, 2017. Defined terms used in this section have the meanings given to them in the accompanying prospectus. If the information in this section differs from the information in the accompanying prospectus, you should rely on the information in this section.

THE KOREA DEVELOPMENT BANK

Unless specified otherwise, the information provided below is stated on a separate basis in accordance with Korean IFRS. Our financial information as of and for the six months ended June 30, 2016 and 2017 in this prospectus supplement is presented based on our unaudited internal management accounts.

Overview

As of June 30, 2017, we hadW142,252.2 billion of loans outstanding (including loans for facility development, loans for working capital, inter-bank loans, private loans,off-shore loan receivables, loans borrowed from overseas financial institutions, bills bought in foreign currencies, advance payments on acceptances and guarantees and other loans without adjusting for allowance for possible loan losses, present value discounts and deferred loan fees), total assets ofW219,308.8 billion and total equity ofW23,420.0 billion, as compared toW141,321.2 billion of loans outstanding,W219,075.9 billion of total assets andW22,565.0 billion of total equity as of December 31, 2016. For the six months ended June 30, 2017, we recorded interest income ofW2,400.6 billion, interest expense ofW1,704.4 billion and net income ofW1,273.1 billion, as compared toW2,588.9 billion of interest income,W1,852.0 billion of interest expense andW289.6 billion of net loss for the six months ended June 30, 2016.

Capitalization

As of June 30, 2017, our authorized capital wasW30,000 billion and capitalization was as follows:

	June 30,  2017(1)
	(billions of won)
	(unaudited)
Long-term debt(2)(3):
Won currency borrowings		3,922.1
Foreign currency borrowings		6,146.3
Industrial finance bonds		113,471.5
Total long-term debt		123,539.9
Capital:
Issued capital		17,793.1
Capital surplus		2,498.7
Capital Adjustment		—
Retained earnings(4)		2,581.6
Accumulated other comprehensive income		546.6
Total capital		23,420.0
Total capitalization		146,959.9

(1) Except as disclosed in this prospectus supplement, there has been no material change in our capitalization since June 30, 2017.

S-8

(2) We have translated borrowings in foreign currencies into Won at the rate ofW1,139.60 to US$1.00, which was the market average exchange rate, as announced by the Seoul Money Brokerage Services Ltd., on June 30, 2017.

(3) As of June 30, 2017, we had contingent liabilities totalingW8,694.0 billion under outstanding guarantees issued on behalf of our clients.

(4) Includes planned regulatory reserve for loan losses ofW1,308.5 billion as of June 30, 2017. If our provision for loan losses is deemed insufficient for regulatory purposes, we compensate for the difference by recording a regulatory reserve for loan losses, which is shown as a separate item included in retained earnings.

Selected Financial Statement Data

The following tables present selected separate financial information as of December 31, 2016 and June 30, 2017 and for the six months ended June 30, 2016 and 2017, which has been derived from our unaudited internal management accounts as of June 30, 2017 and for the six months ended June 30, 2016 and 2017 prepared in accordance with Korean IFRS.

SeparateK-IFRS Financial Statement Data

	Six Months Ended June 30,
	2016			2017
	(billions of won) (unaudited)
Income Statement Data
Total Interest Income		2,588.9			2,400.6
Total Interest Expenses		1,852.0			1,704.4
Net Interest Income		736.9			696.2
Operating Income (Expenses)		(842.6	)		1,838.1
Net Income (Loss)		(289.6	)		1,273.1

	As of December 31, 2016		As of June 30, 2017
	(billions of won)
Statements of Financial Position Data
Total Loans(1)		141,321.2		142,252.2
Total Borrowings(2)		180,357.7		176,644.5
Total Assets		219,075.9		219,308.8
Total Liabilities		196,510.9		195,888.8
Equity		22,565.0		23,420.0

(1) Gross amount, which includes loans for facility development, loans for working capital, inter-bank loans, private loans, off-shore loan receivables, loans borrowed from overseas financial institutions, bills bought in foreign currencies, advance payments on acceptances and guarantees and other loans without adjusting for allowance for loan losses, present value discounts and deferred loan fees.

(2) Total Borrowings include financial liabilities designated at fair value through profit or loss (“FVTPL”), due to customers, borrowings and debt issued.

Six Months Ended June 30, 2017

For the six months ended June 30, 2017, we had net income ofW1,273.1 billion compared to net loss ofW289.6 billion for the six months ended June 30, 2016, on a separate basis.

S-9

Principal factors for the net income ofW1,273.1 billion in the first half of 2017 compared to the net loss ofW289.6 billion in the corresponding period of 2016 included:

• a decrease in provision for loan losses toW716.8 billion in the six months ended June 30, 2017 fromW2,112.7 billion in the corresponding period of 2016, primarily due to (i) thewrite-off during the first half of 2017 of a significant amount of our loans to Hanjin Shipping Co., Ltd. and STX Offshore & Shipbuilding Co., Ltd. and (ii) a decrease in our loans to Daewoo Shipbuilding & Marine Engineering (“DSME”) as a result of adebt-to-equity swap during the first half of 2017; and

• a decrease in provision for acceptances and guarantees toW63.3 billion in the six months ended June 30, 2017 fromW630.7 billion in the corresponding period of 2016, primarily due to a decrease in guarantees as well as an increase in guarantee quality.

The above factors were partially offset by a decrease in dividend income toW706.7 billion in the six months ended June 30, 2017 fromW1,017.6 billion in the corresponding period of 2016, primarily due to decreased dividends from investments in associates (including Korea Electric Power Corporation).

Provisions for Possible Loan Losses and Loans in Arrears

As of June 30, 2017, we established provisions ofW2,983.9 billion for possible loan losses under Korean IFRS. The provisions for possible loan losses under Korean IFRS are recorded for those loans for which objective evidence of impairment exists as a result of one or more events that occurred after initial recognition and, if our provision for possible loan losses is deemed insufficient for regulatory purposes, we compensate for the difference by recording a regulatory reserve for possible loan losses, which will be deducted from retained earnings.

Certain of our customers have restructured loans with their creditor banks. As of June 30, 2017, we have provided loans ofW3,965.1 billion for companies under workout, court receivership, court mediation and other restructuring procedures. In addition, as of such date, we held equity securities of such companies in the amount ofW165.5 billion. As of June 30, 2017, we had established provisions ofW1,674.3 billion for possible loan losses for such companies. We cannot assure you that actual results of the credit loss from the loans to these customers will not exceed the provisions reserved.

The following table provides information on our loan loss provisions.

		As of June 30,  2017(1)
		Loan Amount		Loan  Loss Provisions
		(in billions of won, except percentages)
Loan Classification	Normal(2)	W	133,434.9	W	286.6
	Precautionary		5,324.0		815.7
	Substandard		1,714.7		671.5
	Doubtful		483.3		255.2
	Expected Loss		1,295.3		954.9
	Total(3)	W	142,252.2	W	2,983.9

(1) These figures include loans for facility development, loans for working capital, inter-bank loans, private loans,off-shore loan receivables, loans borrowed from overseas financial institutions, bills bought in foreign currencies, advance payments on acceptances and guarantees and other loans.

(2) Includes loans guaranteed by the Government. Under Korean IFRS, we establish loan loss provisions for all loans including loans guaranteed by the Government.

(3) See note 2 of the notes to our separate financial statements in the accompanying prospectus for a summary of significant accounting policies with respect to impairment of loans.

S-10

As of June 30, 2017, ournon-performing loans totaledW3,493.3 billion, representing 2.5% of our outstanding loans as of such date.Non-performing loans are defined as loans that are classified as substandard or below. On June 30, 2017, our legal reserve was zero due to our use of the reserve to cover our net losses for 2016.

Loans to Financially Troubled Companies

We have credit exposure (including loans, guarantees and equity investments) to a number of financially troubled Korean companies including DSME, STX Offshore & Shipbuilding, Dongbu Steel Co., Ltd. Hanjin Heavy Industries and Construction Co., Ltd., Hyundai Merchant Marine Co., Ltd., Daehan Shipbuilding Co., Ltd., Hanjin Shipping Co., Ltd. and STX Heavy Industries Co., Ltd. As of June 30, 2017, our credit extended to these companies totaledW10,951.6 billion, accounting for 5.0% of our total assets as of such date.

As of June 30, 2017, our exposure (including loans classified as substandard or below and equity investment classified as estimated loss or below) to DSME decreased toW4,935.5 billion fromW7,634.4 billion as of December 31, 2016, primarily due to adebt-to-equity swap and impairment of DSME shares. As of June 30, 2017, our exposure to STX Offshore & Shipbuilding wasW1,115.8 billion, a decrease fromW1,422.8 billion as of December 31, 2016, primarily due to a decrease in guarantees. As of June 30, 2017, our exposure to Dongbu Steel decreased slightly toW1,300.0 billion fromW1,325.2 billion as of December 31, 2016, primarily due to the redemption of certain existing loans. As of June 30, 2017, our exposure to Hanjin Heavy Industries and Construction increased toW1,282.8 billion fromW1,242.2 billion as of December 31, 2016, primarily due to the extension of new loans. As of June 30, 2017, our exposure to Hyundai Merchant Marine decreased toW950.4 billion fromW1,080.4 billion as of December 31, 2016, primarily due to the redemption of certain existing loans. As of June 30, 2017, our exposure to Daehan Shipbuilding decreased toW734.5 billion fromW769.2 billion as of December 31, 2016, primarily due to a decrease in guarantees. As of June 30, 2017, our exposure to Hanjin Shipping decreased toW399.2 billion fromW439.5 billion as of December 31, 2016, primarily due to the redemption of certain existing loans through the sale of collateral. As of June 30, 2017, our exposure to STX Heavy Industries decreased toW233.9 billion fromW268.7 billion as of December 31, 2016, primarily due to a decrease in guarantees.

As of June 30, 2017, we established provisions ofW882.1 billion for our exposure to DSME,W929.0 billion for STX Offshore & Shipbuilding,W157.1 billion for Dongbu Steel,W134.0 billion for Hanjin Heavy Industries and Construction,W188.0 billion for Hyundai Merchant Marine,W89.3 billion for Daehan Shipbuilding,W138.9 billion for Hanjin Shipping andW115.4 billion for STX Heavy Industries.

In the event that the financial condition of these companies or other large corporations to which we extended credits deteriorate in the future, we may be required to record additional provisions for credit losses, as well as charge-offs and valuation or impairment losses or losses on disposal, which may have a material adverse effect on our financial condition and results of operations.

For the six months ended June 30, 2017, we soldnon-performing loans worthW307.6 billion to Eugene Asset Management and UAMCO Ltd.

S-11

Debt

Debt Repayment Schedule

The following table sets out our principal repayment schedule as of June 30, 2017:

Debt Principal Repayment Schedule

Currency(1)(2)(3)	Maturing on or before December 31,
	2017		2018		2019		2020		2021		Thereafter
	(billions of won)
Won	W	25,030.8	W	37,605.2	W	13,687.4	W	1,880.4	W	809.4	W	18,883.6
Foreign		11,825.0		9,073.6		3,903.0		3,067.4		2,262.9		7,756.1
Total Won Equivalent	W	36,855.8	W	46,678.8	W	17,590.4	W	4,947.8	W	3,072.3	W	26,639.7

(1) Excludes bonds sold under repurchase agreements and call money.

(2) Borrowings in foreign currencies have been translated into Won at the market average exchange rates on June 30, 2017, as announced by the Seoul Money Brokerage Services Ltd.

(3) We categorize debt with respect to which we have entered into currency swap agreements by our repayment currency under such agreements.

Directors and Management; Employees

In May 2017, Mr. Chae Yeol Yang was appointed as one of the independent non-executive directors of our Board of Directors. Mr. Yang’s term will expire on May 25, 2019.

In September 2017, Mr. Dong Gull Lee was appointed as our new Chief Executive Officer and Chairman of the Board of Directors.

THE REPUBLIC OF KOREA

Government and Politics

Relations with North Korea

North Korea has continued to develop its nuclear and ballistic missile programs and has engaged in a series of missile tests, including four missiles that were launched in March 2017 and additional missiles launched in May 2017 and July 2017. In response, the United Nations Security Council issued unanimous sanctions on North Korea. On August 29, 2017, North Korea fired a ballistic missile over Japan’s northern island into the Pacific Ocean. In response, the United Nations Security Council condemned North Korea’s firing of the missile and demanded that North Korea cease firing additional missiles and abandon all nuclear weapons and programs. On September 3, 2017, North Korea announced that it successfully conducted its sixth nuclear test by detonating a hydrogen bomb designed to be mounted on an intercontinental ballistic missile, which resulted in increased tensions in the region. In response, on September 11, 2017, the United Nations Security Council unanimously approved a new resolution to further expand economic sanctions against North Korea by imposing a ban on its textile exports and capping imports of crude oil, among others.

There can be no assurance that the level of tension on the Korean peninsula will not escalate in the future or that such escalation will not have a material adverse impact on the Republic’s economy. Any further increase in tension, which may occur, for example, if North Korea experiences a leadership crisis, high-level contacts between the Republic and North Korea break down or military hostilities occur, could have a material adverse effect on the Republic’s economy.

S-12

The Economy

Gross Domestic Product

Based on preliminary data, GDP growth in the first half of 2017 was 2.8% at chained 2010 year prices, as aggregate private and general government consumption expenditures increased by 2.3%, gross domestic fixed capital formation increased by 9.9% and exports of goods and services increased by 1.9%, each compared with the corresponding period of 2016.

Prices, Wages and Employment

The inflation rate was 2.1% in the first quarter of 2017 and 1.9% in the second quarter of 2017. The unemployment rate was 4.3% in the first quarter of 2017 and 3.9% in the second quarter of 2017.

The Financial System

Securities Markets

The Korea Composite Stock Price Index was 2,391.8 on June 30, 2017, 2,402.7 on July 31, 2017, 2,363.2 on August 31, 2017 and 2,359.1 on September 11, 2017.

Monetary Policy

Foreign Exchange

The market average exchange rate between the Won and the U.S. Dollar (in Won per one U.S. Dollar) as announced by the Seoul Money Brokerage Service Ltd. was Won 1,139.6 to US$1.00 on June 30, 2017, Won 1,119.1 to US$1.00 on July 31, 2017, Won 1,122.8 to US$1.00 on August 31, 2017 and Won 1,126.8 to US$1.00 on September 11, 2017.

Balance of Payments and Foreign Trade

Balance of Payments

Based on preliminary data, the Republic recorded a current account surplus of approximately US$36.3 billion in the first half of 2017. The current account surplus in the first half of 2017 decreased from the current account surplus of US$51.7 billion in the corresponding period of 2016, primarily due to an increase in deficit from the services account and a decrease in surplus from the goods account.

Trade Balance

Based on preliminary data, the Republic recorded a trade surplus of US$45.1 billion in the first half of 2017. Exports increased by 15.8% to US$279.3 billion and imports increased by 21.3% to US$234.2 billion from US$241.2 billion of exports and US$193.1 billion of imports, respectively, in the corresponding period of 2016.

Foreign Currency Reserves

The amount of the Government’s foreign currency reserves was US$383.8 billion as of July 31, 2017.

S-13

DESCRIPTION OF THE NOTES

The following is a description of some of the terms of the Notes we are offering. Since it is only a summary, we urge you to read the fiscal agency agreement described below and the forms of global note before deciding whether to invest in the Notes. We have filed a copy of these documents with the United States Securities and Exchange Commission as exhibits to the registration statement no.333-217914.

The general terms of our Notes are described in the accompanying prospectus. The description in this prospectus supplement further adds to that description or, to the extent inconsistent with that description, replaces it.

Governed by Fiscal Agency Agreement

We will issue the 2020 Notes and the Fixed Rate Notes under the fiscal agency agreement, dated as of February 15, 1991, as amended and supplemented from time to time, between us and The Bank of New York (now The Bank of New York Mellon), as fiscal agent (the “Fiscal Agency Agreement”). We will issue the 2022 Notes, which, together with the Original 2022 Notes, will constitute a single series issued under the Fiscal Agency Agreement. The fiscal agent will maintain a register for the Notes.

Payment of Principal and Interest

Floating Rate Notes

The 2020 Notes are initially limited to US$500,000,000 aggregate principal amount. The 2020 Notes will mature on September 19, 2020 (the “2020 Notes Maturity Date”). The 2020 Notes will bear interest at a rate equal to Three-Month USD LIBOR plus 0.675% per annum, payable quarterly in arrears on March 19, June 19, September 19 and December 19 of each year (each a “2020 Notes Interest Payment Date”), beginning on December 19, 2017. Interest on the 2020 Notes will accrue from September 19, 2017. The 2022 Notes offered hereby shall constitute a further issuance of, and be fungible with and be consolidated and form a single series with, the Original 2022 Notes. The total principal amount of the Original 2022 Notes and the 2022 Notes now being issued will be US$650,000,000. The 2022 Notes will mature on February 27, 2022 (the “2022 Notes Maturity Date”, and together with the 2020 Notes Maturity Date, the “Floating Rate Notes Maturity Dates”). The 2022 Notes will bear interest at a rate of 0.705% per annum, payable quarterly in arrears on February 27, May 27, August 27 and November 27 of each year (each a “2022 Notes Interest Payment Date”, and together with the 2020 Notes Interest Payment Date, the “Floating Rate Notes Interest Payment Dates”). The first interest payment on the 2022 Notes will be made on November 27, 2017 in respect of the period from (and including) August 27, 2017 to (but excluding) November 27, 2017. Interest on the 2022 Notes will accrue from August 27, 2017. If any Floating Rate Notes Interest Payment Date or any Floating Rate Notes Maturity Date falls on a day that is not a business day (as defined below), that Floating Rate Notes Interest Payment Date or that Floating Rate Notes Maturity Date will be adjusted in accordance with the Modified Following Business Day Convention. The term “Modified Following Business Day Convention” means that the relevant date shall be postponed to the first following day that is a business day unless that day falls in the next calendar month in which case that date will be the first preceding day that is a business day. The term “business day” as used herein means a day other than a Saturday, a Sunday, or any other day on which banking institutions in The City of New York or Seoul are authorized or required by law or executive order to remain closed.

We will pay interest to the person who is registered as the owner of a Floating Rate Note at the close of business on the fifteenth day (whether or not a business day) preceding such Floating Rate Notes Interest Payment Date. Interest on the Floating Rate Notes will be computed on the basis of the actual number of days in the applicable Interest Period (as defined herein) divided by 360. We will make principal and interest payments on the Floating Rate Notes in immediately available funds in U.S. dollars.

S-14

The term “Three-Month USD LIBOR” means, with respect to any Interest Determination Date (as defined below):

(a) the rate for three-month deposits in United States dollars commencing on the second London Banking Day (as defined below) succeeding the Interest Determination Date, that appears on the Reuters Page LIBOR01 (as defined below) as of 11:00 a.m., London time, on the Interest Determination Date; or

(b) if no rate appears on the particular Interest Determination Date on the Reuters Page LIBOR01, the rate calculated by the Calculation Agent (as defined below) as the arithmetic mean of at least two offered quotations obtained by the Calculation Agent after requesting the principal London offices of each of four major reference banks in the London interbank market to provide the Calculation Agent with its offered quotation for deposits in United States dollars for the period of three months, commencing on the second London Banking Day (as defined below) succeeding the Interest Determination Date, to prime banks in the London interbank market at approximately 11:00 a.m., London time, on that Interest Determination Date and in a principal amount that is representative for a single transaction in United States dollars in that market at that time; or

(c) if fewer than two offered quotations referred to in clause (b) are provided as requested, the rate calculated by the Calculation Agent as the arithmetic mean of the rates quoted at approximately 11:00 a.m., New York time, on the particular Interest Determination Date by three major banks in The City of New York selected by the Calculation Agent for loans in United States dollars to leading European banks for a period of three months commencing on the second London Banking Day succeeding the Interest Determination Date, and in a principal amount that is representative for a single transaction in United States dollars in that market at that time; or

(d) if the banks so selected by the Calculation Agent are not quoting as mentioned in clause (c),Three-Month USD LIBOR in effect immediately prior to the particular Interest Determination Date.

“Reuters Page LIBOR01” means the display on Reuters (or any successor service) on such page (or any other page as may replace such page on such service) or such other service or services as may be nominated by the ICE Benchmark Administration Limited or any successor thereof as the information vendor for the purpose of displaying the London interbank rates of major banks for United States dollars.

“London Banking Day” means a day on which commercial banks are open for business, including dealings in United States dollars, in London, England.

“Interest Determination Date” for any Interest Period will be the second London Banking Day preceding the first day of such Interest Period.

“Interest Period” refers to the period from and including September 19, 2017 to but excluding the first 2020 Notes Interest Payment Date and each successive period from and including a 2020 Notes Interest Payment Date to but excluding the next 2020 Notes Interest Payment Date for the 2020 Notes, and to the period from and including August 27, 2017 to but excluding the first 2022 Notes Interest Payment Date and each successive period from and including a 2022 Notes Interest Payment Date to but excluding the next 2022 Notes Interest Payment Date for the 2022 Notes.

The Bank of New York Mellon will serve as the “Calculation Agent” for the Floating Rate Notes. In the absence of willful default, bad faith or manifest error, the Calculation Agent’s determination of Three-Month USD LIBOR and its calculation of the applicable interest rate for each Interest Period will be final and binding. The Calculation Agent will make available the interest rates for current and preceding Interest Periods by delivery of such notice through such medium as is available to participants in DTC, Euroclear and Clearstream, or any successor thereof, and in accordance with such applicable rules and procedures as long as the Floating Rate Notes are held in global form. In the event that the Floating Rate Notes are held in certificated form, the interest rates for current and preceding Interest Periods will be published in the manner described below under

S-15

“—Notices”. We have the right to replace the Calculation Agent with the London office of another leading commercial bank or investment bank in New York or London. If the appointed office of the Calculation Agent is unable or unwilling to continue to act as the Calculation Agent or fails to determine the interest rate for any Interest Period, we have a duty to appoint the London office of such other leading commercial bank or investment bank in New York or London as may be approved in writing by the fiscal agent.

Fixed Rate Notes

The Fixed Rate Notes are initially limited to US$350,000,000 aggregate principal amount and will mature on March 19, 2023 (the “Fixed Rate Notes Maturity Date”). The Fixed Rate Notes will bear interest at the rate of 2.750% per annum, payable semi-annually in arrears on March 19 and September 19 of each year (each, a “Fixed Rate Notes Interest Payment Date”), beginning on March 19, 2018. Interest on the Fixed Rate Notes will accrue from September 19, 2017. If any Fixed Rate Notes Interest Payment Date or the Fixed Rate Notes Maturity Date shall be a day on which banking institutions in The City of New York or Seoul are authorized or obligated by law to close, then such payment will not be made on such date but will be made on the next succeeding day which is not a day on which banking institutions in The City of New York or Seoul are authorized or obligated by law to close, with the same force and effect as if made on the date for such payment, and no interest shall be payable in respect of any such delay. We will pay interest to the person who is registered as the owner of a Fixed Rate Note at the close of business on the fifteenth day (whether or not a business day) preceding such Fixed Rate Notes Interest Payment Date. Interest on the Fixed Rate Notes will be computed on the basis of a360-day year consisting of twelve30-day months. We will make principal and interest payments on the Fixed Rate Notes in immediately available funds in U.S. dollars.

The payment of interest and the repayment of principal on the Notes will not be guaranteed by the Government.

Denomination

The Notes will be issued in minimum denominations of US$200,000 principal amount and integral multiples of US$1,000 in excess thereof.

Redemption

We may not redeem the Notes prior to maturity. At maturity, we will redeem the Notes at par.

Form and Registration

We will issue each series of the Notes in the form of one or more fully registered global notes, registered in the name of a nominee of and deposited with the custodian for DTC. Except as described in the accompanying prospectus under “Description of the Securities—Description of Debt Securities—Global Securities,” the global notes will not be exchangeable for Notes in definitive registered form, and will not be issued in definitive registered form. Financial institutions, acting as direct and indirect participants in DTC, will represent your beneficial interests in the global notes. These financial institutions will record the ownership and transfer of your beneficial interest through book-entry accounts. You may hold your beneficial interests in the Notes through Euroclear or Clearstream if you are a participant in such systems, or indirectly through organizations that are participants in such systems. Any secondary market trading of book-entry interests in the Notes will take place through DTC participants, including Euroclear and Clearstream. See “Clearance and Settlement—Transfers Within and Between DTC, Euroclear and Clearstream.”

The fiscal agent will not charge you any fees for the Notes, other than reasonable fees for the replacement of lost, stolen, mutilated or destroyed Notes. However, you may incur fees for the maintenance and operation of the book-entry accounts with the clearing systems in which your beneficial interests are held.

S-16

For so long as the Notes are listed on theSGX-ST and the rules of theSGX-ST so require, in the event that the global notes are exchanged for Notes in definitive registered form, we will appoint and maintain a paying agent in Singapore, where the certificates representing the Notes may be presented or surrendered for payment or redemption (if required). In addition, in the event that the global notes are exchanged for Notes in definitive registered form, an announcement of such exchange will be made through theSGX-ST by or on behalf of the issuer. Such announcement will include all material information with respect to the delivery of the definitive Notes, including details of the paying agent in Singapore.

Further Issues

We may from time to time, without the consent of the holders of the Notes, create and issue additional debt securities with the same terms and conditions as either series of the Notes in all respects so that such further issue shall be consolidated and form a single series with the relevant series of the Notes. We will not issue any such additional debt securities unless such additional securities have no more than a de minimis amount of original issue discount or such issuance would otherwise constitute a “qualified reopening” for U.S. federal income tax purposes.

Notices

All notices regarding the Notes will be published in London in the Financial Times and in New York in The Wall Street Journal (U.S. Edition). If we cannot, for any reason, publish notice in any of those newspapers, we will choose an appropriate alternate English language newspaper of general circulation, and notice in that newspaper will be considered valid notice. Notice will be considered made on the first date of its publication.

S-17

CLEARANCE AND SETTLEMENT

We have obtained the information in this section from sources we believe to be reliable, including DTC, Euroclear and Clearstream. We accept responsibility only for accurately extracting information from such sources. DTC, Euroclear and Clearstream are under no obligation to perform or continue to perform the procedures described below, and they may modify or discontinue them at any time. Neither we nor the registrar will be responsible for DTC’s, Euroclear’s or Clearstream’s performance of their obligations under their rules and procedures. Nor will we or the registrar be responsible for the performance by direct or indirect participants of their obligations under their rules and procedures.

Introduction

The Depository Trust Company

DTC is:

• a limited-purpose trust company organized under the New York Banking Law;

• a “banking organization” under the New York Banking Law;

• a member of the Federal Reserve System;

• a “clearing corporation” under the New York Uniform Commercial Code; and

• a “clearing agency” registered under Section 17A of the Securities Exchange Act of 1934.

DTC was created to hold securities for its participants and facilitate the clearance and settlement of securities transactions between its participants. It does this through electronic book-entry changes in the accounts of its direct participants, eliminating the need for physical movement of securities certificates.

Euroclear and Clearstream

Like DTC, Euroclear and Clearstream hold securities for their participants and facilitate the clearance and settlement of securities transactions between their participants through electronic book-entry changes in their accounts. Euroclear and Clearstream provide various services to their participants, including the safekeeping, administration, clearance and settlement and lending and borrowing of internationally traded securities. Participants in Euroclear and Clearstream are financial institutions such as underwriters, securities brokers and dealers, banks and trust companies. Some of the underwriters participating in this offering are participants in Euroclear or Clearstream. Other banks, brokers, dealers and trust companies have indirect access to Euroclear or Clearstream by clearing through or maintaining a custodial relationship with a Euroclear or Clearstream participant.

Ownership of the Notes through DTC, Euroclear and Clearstream

We will issue each series of the Notes in the form of one or more fully registered global notes, registered in the name of a nominee of DTC. Financial institutions, acting as direct and indirect participants in DTC, will represent your beneficial interests in the Notes. These financial institutions will record the ownership and transfer of your beneficial interests through book-entry accounts. You may also hold your beneficial interests in the Notes through Euroclear or Clearstream, if you are a participant in such systems, or indirectly through organizations that are participants in such systems. Euroclear and Clearstream will hold their participants’ beneficial interests in the global notes in their customers’ securities accounts with their depositaries. These depositaries of Euroclear and Clearstream in turn will hold such interests in their customers’ securities accounts with DTC.

We and the fiscal agent generally will treat the registered holder of the Notes, initially Cede & Co., as the absolute owner of the Notes for all purposes. Once we and the fiscal agent make payments to the registered

S-18

holder, we and the fiscal agent will no longer be liable on the Notes for the amounts so paid. Accordingly, if you own a beneficial interest in the global notes, you must rely on the procedures of the institutions through which you hold your interests in the Notes, including DTC, Euroclear, Clearstream and their respective participants, to exercise any of the rights granted to holders of the Notes. Under existing industry practice, if you desire to take any action that Cede & Co., as the holder of the global notes, is entitled to take, then Cede & Co. would authorize the DTC participant through which you own your beneficial interest to take such action. The participant would then either authorize you to take the action or act for you on your instructions.

DTC may grant proxies or authorize its participants, or persons holding beneficial interests in the Notes through such participants, to exercise any rights of a holder or take any actions that a holder is entitled to take under the Fiscal Agency Agreement or the Notes. Euroclear’s or Clearstream’s ability to take actions as holder under the Notes or the Fiscal Agency Agreement will be limited by the ability of their respective depositaries to carry out such actions for them through DTC. Euroclear and Clearstream will take such actions only in accordance with their respective rules and procedures.

Transfers Within and Between DTC, Euroclear and Clearstream

Trading Between DTC Purchasers and Sellers

DTC participants will transfer interests in the Notes among themselves in the ordinary way according to DTC rules. Participants will pay for such transfers by wire transfer. The laws of some states require certain purchasers of securities to take physical delivery of the securities in definitive form. These laws may impair your ability to transfer beneficial interests in the global notes to such purchasers. DTC can act only on behalf of its direct participants, who in turn act on behalf of indirect participants and certain banks. Thus, your ability to pledge a beneficial interest in the global notes to persons that do not participate in the DTC system, and to take other actions, may be limited because you will not possess a physical certificate that represents your interest.

Trading Between Euroclear and/or Clearstream Participants

Participants in Euroclear and Clearstream will transfer interests in the Notes among themselves according to the rules and operating procedures of Euroclear and Clearstream.

Trading Between a DTC Seller and a Euroclear or Clearstream Purchaser

When the Notes are to be transferred from the account of a DTC participant to the account of a Euroclear or Clearstream participant, the purchaser must first send instructions to Euroclear or Clearstream through a participant at least one business day prior to the settlement date. Euroclear or Clearstream will then instruct its depositary to receive the Notes and make payment for them. On the settlement date, the depositary will make payment to the DTC participant’s account, and the Notes will be credited to the depositary’s account. After settlement has been completed, DTC will credit the Notes to Euroclear or Clearstream, Euroclear or Clearstream will credit the Notes, in accordance with its usual procedures, to the participant’s account, and the participant will then credit the purchaser’s account. These securities credits will appear the next day (European time) after the settlement date. The cash debit from the account of Euroclear or Clearstream will be back-valued to the value date, which will be the preceding day if settlement occurs in New York. If settlement is not completed on the intended value date (i.e., the trade fails), the cash debit will instead be valued at the actual settlement date.

Participants in Euroclear and Clearstream will need to make funds available to Euroclear or Clearstream to pay for the Notes by wire transfer on the value date. The most direct way of doing this is topre-position funds (i.e., have funds in place at Euroclear or Clearstream before the value date), either from cash on hand or existing lines of credit. Under this approach, however, participants may take on credit exposure to Euroclear and Clearstream until the Notes are credited to their accounts one day later.

As an alternative, if Euroclear or Clearstream has extended a line of credit to a participant, the participant may decide not topre-position funds, but to allow Euroclear or Clearstream to draw on the line of credit to

S-19

finance settlement for the Notes. Under this procedure, Euroclear or Clearstream would charge the participant overdraft charges for one day, assuming that the overdraft would be cleared when the Notes were credited to the participant’s account. However, interest on the Notes would accrue from the value date. Therefore, in many cases the interest income on the Notes which the participant earns during thatone-day period will substantially reduce or offset the amount of the participant’s overdraft charges. Of course, this result will depend on the cost of funds (i.e., the interest rate that Euroclear or Clearstream charges) to each participant.

Since the settlement will occur during New York business hours, a DTC participant selling an interest in the Notes can use its usual procedures for transferring global securities to the depositories of Euroclear or Clearstream for the benefit of Euroclear or Clearstream participants. The DTC seller will receive the sale proceeds on the settlement date. Thus, to the DTC seller, a cross-market sale will settle no differently than a trade between two DTC participants.

Finally, day traders who use Euroclear or Clearstream and who purchase Notes from DTC participants for credit to Euroclear participants or Clearstream participants should note that these trades will automatically fail unless one of three steps is taken:

• borrowing through Euroclear or Clearstream for one day, until the purchase side of the day trade is reflected in the day trader’s Euroclear or Clearstream account, in accordance with the clearing system’s customary procedures;

• borrowing the Notes in the United States from DTC participants no later than one day prior to settlement, which would allow sufficient time for the Notes to be reflected in the Euroclear or Clearstream account in order to settle the sale side of the trade; or

• staggering the value dates for the buy and sell sides of the trade so that the value date for the purchase from the DTC participant is at least one day prior to the value date for the sale to the Euroclear or Clearstream participant.

Trading Between a Euroclear or Clearstream Seller and a DTC Purchaser

Due to time-zone differences in their favor, Euroclear and Clearstream participants can use their usual procedures to transfer Notes through their depositaries to a DTC participant. The seller must first send instructions to Euroclear or Clearstream through a participant at least one business day prior to the settlement date. Euroclear or Clearstream will then instruct its depositary to credit the Notes to the DTC participant’s account and receive payment. The payment will be credited in the account of the Euroclear or Clearstream participant on the following day, but the receipt of the cash proceeds will be back-valued to the value date, which will be the preceding day if settlement occurs in New York. If settlement is not completed on the intended value date (i.e., the trade fails), the receipt of the cash proceeds will instead be valued at the actual settlement date.

If the Euroclear or Clearstream participant selling the Notes has a line of credit with Euroclear or Clearstream and elects to be in debit for the Notes until it receives the sale proceeds in its account, then the back-valuation may substantially reduce or offset any overdraft charges that the participant incurs over that period.

Settlement in other currencies between DTC and Euroclear and Clearstream is possible usingfree-of-payment transfers to move the Notes, but funds movement will take place separately.

S-20

TAXATION

Korean Taxation

For a discussion of certain Korean tax considerations that may be relevant to you if you invest in the Notes, see “Taxation—Korean Taxation” in the accompanying prospectus.

United States Tax Considerations

We expect that the issue price of the Notes (excluding amounts paid in respect of accrued interest) will reflect no more than ade minimis amount of original issue discount. In that case, the 2022 Notes will be treated for U.S. federal income tax purposes as part of the same issue as the Original 2022 Notes.

Any pre-issuance accrued interest will be included in the accrued interest to be paid on the 2022 Notes on the first interest payment date after the issuance of the 2022 Notes. The portion of the first stated interest payment equal to the pre-issuance accrued interest will be deemed to be a non-taxable return of pre-issuance accrued interest and, accordingly, will not be taxable as interest on the 2022 Notes. If the price you pay for the 2022 Notes (excluding amounts paid in respect of pre-issuance accrued interest not included in income, as described above) exceeds the principal amount of the 2022 Notes, then you will be considered to have purchased the 2022 Notes at a premium, and you may elect to amortize the premium as an offset to interest income as discussed in “Taxation—United States Tax Considerations—Premium and Market Discount” in the accompanying prospectus.

For a discussion of additional U.S. federal income tax considerations that may be relevant to you if you invest in the Notes and are a U.S. holder, see “Taxation—United States Tax Considerations” in the accompanying prospectus.

S-21

UNDERWRITING

Relationship with the Underwriters

We and the underwriters named below (the “Underwriters”) have entered into a Terms Agreement dated September 12, 2017 (the “Terms Agreement”) with respect to the Notes relating to the Underwriting Agreement—Standard Terms (together with the Terms Agreement, the “Underwriting Agreement”) filed as an exhibit to the registration statement. Subject to the terms and conditions set forth in the Underwriting Agreement, we have agreed to sell to each of the Underwriters, severally and not jointly, and each of the Underwriters has, severally and not jointly, agreed to purchase, the following principal amount of the Notes set out opposite its name below:

Name of Underwriters	Principal Amount of the 2020 Notes		Principal Amount of the 2022 Notes		Principal Amount of the Fixed Rate Notes
Goldman Sachs International	US$	71,429,000	US$	21,428,000	US$	50,000,000
KDB Asia Limited		71,429,000		21,428,000		50,000,000
Mirae Asset Daewoo Co., Ltd.		71,429,000		21,428,000		50,000,000
Mizuho Securities USA LLC		71,428,000		21,429,000		50,000,000
Morgan Stanley & Co. International plc		71,429,000		21,429,000		50,000,000
Société Générale		71,428,000		21,429,000		50,000,000
UBS AG Hong Kong Branch		71,428,000		21,429,000		50,000,000
	US$	500,000,000	US$	150,000,000	US$	350,000,000

KDB Asia Limited, one of the underwriters, is our affiliate and has agreed to offer and sell the Notes only outside the United States to non-U.S. persons.

Under the terms and conditions of the Underwriting Agreement, if the Underwriters take any series of the Notes, then the Underwriters are obligated to take and pay for all of the Notes of such series.

The Underwriters initially propose to offer the Notes directly to the public at the offering price described on the cover page of this prospectus supplement. After the initial offering of the Notes, the Underwriters may from time to time vary the offering price and other selling terms.

If a jurisdiction requires that the offering be made by a licensed broker or dealer and the Underwriters or any affiliate of the Underwriters is a licensed broker or dealer in that jurisdiction, the offering shall be deemed to be made by that Underwriter or its affiliate on our behalf in such jurisdiction.

The Notes are a new class of securities with no established trading market. Applications will be made to the SGX-ST for the listing and quotation of the Notes. The Underwriters have advised us that they intend to make a market in the Notes. However, they are not obligated to do so and they may discontinue any market making activities with respect to the Notes at any time without notice. Accordingly, we cannot assure you as to the liquidity of any trading market for the Notes.

We have agreed to indemnify the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended, or to contribute to payments which the Underwriters may be required to make in respect of any such liabilities.

The amount of net proceeds from our 2020 Notes is US$498,500,000 after deducting underwriting discounts but not estimated expenses. Expenses associated with the 2020Notes offering are estimated to be US$70,000. The Underwriters have agreed to pay certain of our expenses incurred in connection with the offering of the 2020 Notes.

S-22

The amount of net proceeds from our 2022 Notes is US$148,948,500 after deducting underwriting discounts but not estimated expenses. Expenses associated with the 2022Notes offering are estimated to be US$70,000. The Underwriters have agreed to pay certain of our expenses incurred in connection with the offering of the 2022 Notes.

The amount of net proceeds from our Fixed Rate Notes is US$348,862,500 after deducting underwriting discounts but not estimated expenses. Expenses associated with the Fixed Rate Notes offering are estimated to be US$70,000. The Underwriters have agreed to pay certain of our expenses incurred in connection with the offering of the Fixed Rate Notes.

The Underwriters and certain of their affiliates may have performed certain commercial banking, investment banking and advisory services for us and/or our affiliates from time to time for which they have received customary fees and expenses and may, from time to time, engage in transactions with and perform services for us and/or our affiliates in the ordinary course of their business.

The Underwriters or certain of their affiliates may purchase Notes and be allocated Notes for asset management and/or proprietary purposes but not with a view to distribution. The Underwriters or their respective affiliates may purchase Notes for its or their own account and enter into transactions, including credit derivatives, such as asset swaps, repackaging and credit default swaps relating to Notes and/or other securities of us or our subsidiaries or affiliates at the same time as the offer and sale of Notes or in secondary market transactions. Such transactions would be carried out as bilateral trades with selected counterparties and separately from any existing sale or resale of Notes to which this prospectus supplement relates (notwithstanding that such selected counterparties may also be purchasers of Notes).

Delivery of the Notes

We expect to make delivery of the Notes, against payment insame-day funds on or about September 19, 2017, which we expect will be the fifth business day following the date of this prospectus supplement. Under Rule 15c6-1 promulgated under the Securities Exchange Act of 1934, as amended, U.S. purchasers are generally required to settle trades in the secondary market in two business days, unless they and the other parties to any such trade expressly agree otherwise. Accordingly, if you wish to trade in the Notes on any day prior to the second business day from the settlement, because the Notes will initially settle in T+5, you may be required to specify an alternate settlement cycle at the time of your trade to prevent a failed settlement. Purchasers in other countries should consult with their own advisors.

Foreign Selling Restrictions

Each Underwriter has agreed, severally and not jointly, to the following selling restrictions in connection with the offering with respect to the following jurisdictions:

Korea

Each Underwriter has severally represented and agreed that (i) it has not offered, sold or delivered and will not offer, sell or deliver, directly or indirectly, any Notes in Korea, or to, or for the account or benefit of, any resident of Korea, except as otherwise permitted by applicable Korean laws and regulations, and (ii) any securities dealer to whom the Underwriters may sell the Notes will agree that it will not offer any Notes, directly or indirectly, in Korea, or to any resident of Korea, except as permitted by applicable Korean laws and regulations, or to any other dealer who does not so represent and agree.

United Kingdom

Each Underwriter has severally represented and agreed that (i) it has only communicated or caused to be communicated and will only communicate or cause to be communicated any invitation or inducement to engage

S-23

in investment activity (within the meaning of Section 21 of the Financial Services and Markets Act of 2000 (the “FSMA”)) received by it in connection with the issue or sale of any of the Notes in circumstances in which section 21(1) of the FSMA does not apply to us, and (ii) it has complied, and will comply with, all applicable provisions of the FSMA with respect to anything done by it in relation to the Notes, from or otherwise involving the United Kingdom.

Japan

Each Underwriter has severally represented and agreed that the Notes have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948, as amended); it has not offered or sold, and it will not offer or sell, directly or indirectly, any of the Notes in Japan or to, or for the account or benefit of, any resident of Japan or to, or for the account or benefit of, any resident for reoffering or resale, directly or indirectly, in Japan or to, or for the account or benefit of, any resident of Japan except (i) pursuant to an exemption from the registration requirements of, or otherwise in compliance with, the Financial Instruments and Exchange Law of Japan, and (ii) in compliance with the other relevant laws of Japan.

Hong Kong

Each Underwriter has severally represented and agreed that:

• it has not offered or sold and will not offer or sell in Hong Kong, by means of any document, any Notes other than (i) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571 of the Laws of Hong Kong) (the “SFO”) and any rules made under the SFO; or (ii) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies (Winding Up and Miscellaneous Provisions) Ordinance (Cap. 32 of the Laws of Hong Kong) (the “Companies Ordinance”) or which do not constitute an offer to the public within the meaning of the Companies Ordinance; and

• it has not issued, or had in its possession for the purposes of issue, and will not issue or have in its possession for the purposes of issue, any advertisement, invitation or document relating to the Notes, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are or are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to Notes which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the SFO and any rules made thereunder.

Singapore

Each Underwriter has severally represented and agreed that neither the preliminary prospectus nor the prospectus has been or will be registered as a prospectus with the Monetary Authority of Singapore under the Securities and Futures Act (Chapter 289 of Singapore)(the “SFA”). Accordingly, each Underwriter has severally represented, warranted and agreed that it has not offered or sold any Notes or caused the Notes to be made the subject of an invitation for subscription or purchase and will not offer or sell any Notes or cause the Notes to be made the subject of an invitation for subscription or purchase, and has not circulated or distributed, nor will it circulate or distribute, the preliminary prospectus or the prospectus or any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the Notes, whether directly or indirectly, to any person in Singapore other than (i) to an institutional investor (as defined in Section 4A of the SFA) pursuant to Section 274 of the SFA, (ii) to a relevant person pursuant to Section 275(1) of the SFA, or any person pursuant to an offer referred to in Section 275(1A) of the SFA, and in accordance with the conditions specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

S-24

Where the Notes are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

(a) a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

(b) a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor,

securities (as defined in Section 239(1) of the SFA) of that corporation or the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferred within 6 months after that corporation or that trust has acquired the Notes pursuant to an offer made under Section 275 of the SFA except:

(1) to an institutional investor or to a relevant person defined in Section 275(2) of the SFA, or to any person arising from an offer referred to in Section 275(1A) or Section 276(4)(i)(B) of the SFA;

(2) where no consideration is or will be given for the transfer;

(3) where the transfer is by operation of law;

(4) as specified in Section 276(7) of the SFA; or

(5) as specified in Regulation 32 of the Securities and Futures (Offers of Investments) (Shares and Debentures) Regulations 2005 of Singapore.

Australia

No prospectus or other disclosure document (as defined in the Corporations Act 2001 of Australia) in relation to the offering of the Notes has been or will be lodged with or registered by Australian Securities and Investments Commission or the Australian Securities Exchange Limited. Each Underwriter has represented and agreed that it has not:

(a) made or invited, and will not make or invite, an offer of the Notes for issue or sale in Australia (including an offer or invitation which is received by a person in Australia); and

(b) distributed or published and will not distribute or publish any draft, preliminary or final form offering memorandum, advertisement or other offering material relating to the Notes in Australia,

unless:

(i) the minimum aggregate consideration payable by each offeree is at least AUD 500,000 (or its equivalent in an alternate currency) (disregarding money lent by the offeror or its associates) or the offer otherwise does not require disclosure to investors in accordance with Part 6D.2 and Part 7 of the Corporations Act 2001 of Australia; and

(ii) such action complies with all applicable laws, directives and regulations and does not require any document to be lodged with, or registered by, the Australian Securities and Investments Commission.

Each Underwriter has agreed that it will not sell the Notes in circumstances where employees of the Underwriter aware of, or involved in, the sale know, or have reasonable grounds to suspect, that the Notes, or an interest in or right in respect of the Notes, was being, or would later be, acquired either directly or indirectly by a resident of Australia, or a non-resident who is engaged in carrying on business in Australia at or through a permanent establishment of that non-resident in Australia (the expressions “resident of Australia”, “non-resident” and “permanent establishment” having the meanings given to them by the Australian Tax Act).

Canada

Prospective Canadian investors are advised that the information contained within the preliminary prospectus and prospectus has not been prepared with regard to matters that may be of particular concern to Canadian

S-25

investors. Accordingly, prospective Canadian investors should consult with their own legal, financial and tax advisers concerning the information contained within the preliminary prospectus and prospectus and as to the suitability of an investment in the Notes in their particular circumstances.

Each Underwriter has severally represented and agreed that the Notes may only be offered or sold in the provinces of Alberta, British Columbia, Ontario and Québec or to or for the benefit of a resident of these provinces pursuant to an exemption from the requirement to file a prospectus in such province in which such offer or sale is made, and only by a dealer duly registered under the applicable securities laws of that province or by a dealer that is relying in that province on the “international dealer” exemption provided by section 8.18 of National Instrument 31-103Registration Requirements,Exemptions and Ongoing Registrant Obligations (NI 31-103). Furthermore, the Notes may only be offered or sold to or for the benefit of a resident of any such province provided that such resident is both an “accredited investor” as defined in National Instrument 45-106Prospectus Exemptions (NI 45-106) or subsection 73.3 (1) of theSecurities Act (Ontario) and a “permitted client” as defined in NI 31-103. By purchasing any Notes and accepting delivery of a purchase confirmation a purchaser is representing to the underwriters and the dealer from whom the purchase confirmation is received that it is an “accredited investor” and “permitted client” as defined above. The distribution of the Notes in Canada is being made on a private placement basis only and any resale of the Notes must be made in accordance with applicable Canadian securities laws, which will vary depending on the relevant jurisdiction, and which may require resales to be made in accordance with prospectus and registration requirements or exemptions from the prospectus and registration requirements.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this preliminary prospectus or prospectus (including any amendment hereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Under Canadian securities law, National Instrument 33-105Underwriting Conflicts (NI 33-105) provides disclosure requirements with respect to potential conflicts of interest between an issuer and underwriters, dealers or placement agents, as the case may be. To the extent any conflict of interest between us and any of the Underwriters (or any other placement agent acting in connection with this offering) may exist in respect of this offering, the applicable parties to this offering are relying on the exemption from these disclosure requirements provided to them by section 3A.3 of NI 33-105 (exemption based on U.S. disclosure).

We and the Underwriters hereby notify prospective Canadian purchasers that: (a) we may be required to provide personal information pertaining to the purchaser as required to be disclosed in Schedule I ofForm 45-106F1 under NI 45-106 (including its name, address, telephone number and the aggregate purchase price of any Notes purchased) (“personal information”), which Form 45-106F1 may be required to be filed by us under NI 45-106, (b) such personal information may be delivered to the Ontario Securities Commission (the “OSC”) in accordance with NI 45-106, (c) such personal information is collected indirectly by the OSC under the authority granted to it under the securities legislation of Ontario, (d) such personal information is collected for the purposes of the administration and enforcement of the securities legislation of Ontario, and (e) the public official in Ontario who can answer questions about the OSC’s indirect collection of such personal information is the Administrative Support Clerk at the OSC, Suite 1903, Box 55, 20 Queen Street West, Toronto, Ontario M5H 3S8, Telephone: (416) 593-3684. Prospective Canadian purchasers that purchase Notes in this offering will be deemed to have authorized the indirect collection of the personal information by the OSC, and to have acknowledged and consented to its name, address, telephone number and other specified information, including the aggregate purchase price paid by the purchaser, being disclosed to other Canadian securities regulatory authorities, and to have acknowledged that such information may become available to the public in accordance with requirements of applicable Canadian laws.

S-26

Upon receipt of this prospectus, each Canadian purchaser hereby confirms that it has expressly requested that all documents evidencing or relating in any way to the sale of the securities described herein (including for greater certainty any purchase confirmation or any notice) be drawn up in the English language only.Par la réception de ce prospectus, chaque acheteur canadien confirme par les présentes qu’il a expressément exigé que tous les documents faisant foi ou se rapportant de quelque manière que ce soit à la vente des valeurs mobilières décrites aux présentes (incluant, pour plus de certitude, toute confirmation d’achat ou tout avis) soient rédigés en anglais seulement.

Price Stabilization and Short Position

In connection with this offering, Morgan Stanley & Co. International plc (the “Stabilizing Manager”) or any person acting for it, on behalf of the Underwriters, may purchase and sell the Notes in the open market. These transactions may include over-allotment, covering transactions, penalty bids and stabilizing transactions. Over-allotment involves sales of the Notes in excess of the principal amount of Notes to be purchased by the Underwriters in this offering, which creates a short position for the Underwriters. Covering transactions involve purchases of the Notes in the open market after the distribution has been completed in order to cover short positions. A penalty bid occurs when a particular Underwriter repays to the Underwriters a portion of the underwriting discount received by it because the Underwriters or the Stabilizing Manager has repurchased Notes sold by or for the account of such Underwriter in stabilizing or short covering transactions. Stabilizing transactions consist of certain bids or purchases of Notes in the open market for the purpose of preventing or retarding a decline in the market price of the Notes while the offering is in progress. Any of these activities may have the effect of preventing or retarding a decline in the market price of the Notes. They may also cause the price of the Notes to be higher than the price that otherwise would exist in the open market in the absence of these transactions. The Stabilizing Manager may conduct these transactions in theover-the-counter market or otherwise. If the Stabilizing Manager commences any of these transactions, it may discontinue them at any time, and must discontinue them after a limited period.

S-27

LEGAL MATTERS

The validity of the Notes is being passed upon for us by Cleary Gottlieb Steen & Hamilton LLP, New York, New York, and by Lee & Ko, Seoul, Korea. Certain legal matters will also be passed upon for the Underwriters by Davis Polk & Wardwell LLP, New York, New York. In giving their opinions, Cleary Gottlieb Steen & Hamilton LLP and Davis Polk & Wardwell LLP may rely as to matters of Korean law upon the opinions of Lee & Ko, and Lee & Ko may rely as to matters of New York law upon the opinions of Cleary Gottlieb Steen & Hamilton LLP.

OFFICIAL STATEMENTS AND DOCUMENTS

Our Chief Executive Officer and Chairman of the Board of Directors, in his official capacity, has supplied the information set forth in this prospectus supplement under “Recent Developments—The Korea Development Bank.” Such information is stated on his authority. The documents identified in the portion of this prospectus supplement captioned “Recent Developments—The Republic of Korea” as the sources of financial or statistical data are derived from official public documents of the Republic and of its agencies and instrumentalities.

GENERAL INFORMATION

We were established in 1954 as a government-owned financial institution pursuant to The Korea Development Bank Act, as amended. The address of our registered office is 14, Eunhaeng-ro,Yeongdeungpo-gu, Seoul 07242, The Republic of Korea.

Our Board of Directors can be reached at the address of our registered office: c/o 14, Eunhaeng-ro,Yeongdeungpo-gu, Seoul 07242, The Republic of Korea.

The issue of the Notes has been authorized by a resolution of our Board of Directors passed on December 29, 2016 and a decision of our Chief Executive Officer and Chairman of the Board of Directors dated August 30, 2017. On September 4, 2017, we filed our reports on the proposed issuance of the Notes with the Ministry of Strategy and Finance of Korea.

The registration statement with respect to us and the Notes has been filed with the U.S. Securities and Exchange Commission in Washington, D.C. under the Securities Act of 1933, as amended. Additional information concerning us and the Notes is contained in the registration statement and post-effective amendments to such registration statement, including their various exhibits, which may be inspected at the public reference facilities maintained by the Securities and Exchange Commission at Room 1580, 100 F Street N.E., Washington, D.C. 20549, United States.

The Notes have been accepted for clearance through DTC, Euroclear and Clearstream:

	ISIN		CUSIP		Common Code
2020 Notes		US500630CR79		500630 CR7		168264186
2022 Notes		US500630CN65		500630 CN6		157232061
Fixed Rate Notes		US500630CS52		500630 CS5		168264208

S-28

HEAD OFFICE OF THE BANK

14, Eunhaeng-ro

Yeongdeungpo-gu, Seoul 07242

The Republic of Korea

FISCAL AGENT AND PRINCIPAL PAYING AGENT

The Bank of New York Mellon

101 Barclay Street, 21^st Floor West

New York, NY 10286

United States of America

LEGAL ADVISORS TO THE BANK

as to Korean law	as to U.S. law
Lee & Ko Seyang Building 39, Sajik-ro 8-gil, Jongno-gu Seoul 03170 The Republic of Korea	Cleary Gottlieb Steen & Hamilton LLP c/o 19th Floor, Ferrum Tower 19 Eulji-ro 5-gil, Jung-gu Seoul 04539 The Republic of Korea

LEGAL ADVISOR TO THE UNDERWRITERS

as to U.S. law

Davis Polk & Wardwell LLP

c/o 18th Floor

The Hong Kong Club Building

3A Chater Road

Hong Kong

AUDITOR OF THE BANK

KPMG Samjong Accounting Corp.

10^th Floor, Gangnam Finance Center

152, Teheran-ro

Gangnam-gu, Seoul 06236

The Republic of Korea

SINGAPORE LISTING AGENT

Shook Lin & Bok LLP

1 Robinson Road

#18-00 AIA Tower

Singapore 048542