FIVE STAR SENIOR LIVING INC. 2018 Proxy Statement    1

VOTING INFORMATIONTable of Contents

WE WANT TO HEAR FROM YOU –PLEASE VOTE TODAY

YourPlease vote is important.

ELIGIBILITY TO VOTE

You canto play a part in our future. The Nasdaq Stock Market LLC (the "Nasdaq") rules do not allow a broker, bank or other nominee who holds shares on your behalf to vote if you were a stockholder of record at the close of business on February 23, 2018.nondiscretionary matters without your instructions.

PROPOSALS THAT REQUIRE YOUR VOTE

You can vote in advance in one of three ways:

via the internet		Visitwww.proxyvote.com and enter your 16 digit16-digit control number provided in your Notice Regarding the Availability of Proxy Materials, proxy card or voting instruction form before 11:59 p.m., Eastern time, on May 16, 2018June 7, 2021 to authorize a proxyVIA THE INTERNET.
by phone		Call 1-800-690-6903 if you are a stockholder of record and 1-800-454-8683 if you are a beneficial owner before 11:59 p.m., Eastern time, on May 16, 2018June 7, 2021 to authorize a proxyBY TELEPHONE. You will need the 16 digit16-digit control number provided on your Notice Regarding the Availability of Proxy Materials, proxy card or voting instruction form.
by mail		Sign, date and return your proxy card if you are a stockholder of record or voting instruction form if you are a beneficial owner to authorize a proxyBY MAIL.

If the meeting is postponed or adjourned, these times will be extended to 11:59 p.m., Eastern time, on the day before the reconvened meeting.

PLEASE VISIT:www.proxyvote.com

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ReviewTo review and download easy to read versions of our Proxy Statement and Annual Report.



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SignTo sign up for future electronic delivery to reduce the impact on the environment.

2    FIVE STAR SENIOR LIVING INC. 2018 Proxy Statement

SUMMARY OF PROPOSALS

This summary highlights matters for consideration by stockholders at our 2018 Annual Meeting. You should read this entire Proxy Statement carefully before voting. Page references are supplied to help you find further information in this Proxy Statement.

BOARD NOMINEES (page 14)

The following two Directors are up for election to our Company's Board of Directors.

RATIFICATION OF THE APPOINTMENT OF RSM US LLP AS INDEPENDENT AUDITORS (page 53)

Stockholders are asked to ratify the appointment of RSM US LLP as independent auditors of Five Star Senior Living Inc. for the Company's fiscal year ending December 31, 2018. The Company's Audit Committee evaluates the performance of the Company's independent auditors and determines whether to reengage the current independent auditors or consider other audit firms. In doing so, the Audit Committee considers the quality and efficiency of the services provided by the auditors, the auditors' technical expertise and knowledge of the Company's operations and industry, the auditors' independence, legal proceedings involving the auditors, the results of PCAOB inspections and peer quality reviews of the auditors and the auditors' reputation in the marketplace. Based on its consideration of these matters, the Audit Committee has appointed RSM US LLP to serve as the Company's independent auditors for the fiscal year ending December 31, 2018.

FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement    31

Table of Contents

400 CENTRE STREET
NEWTON, MASSACHUSETTS 02458April 7, 2021

March 22, 2018

PROXY STATEMENT

The Board of Directors (the(our "Board") is furnishing this Proxy Statement to solicit proxies to be voted at the 2018 Annual Meeting of Stockholders (the "2018 Annual Meeting") of Five Star Senior Living Inc., a Maryland corporation (together with its direct or indirect subsidiaries, the(the "Company," "we," "us" or "our"). The is furnishing this proxy statement (the "Proxy Statement") and accompanying proxy card (or voting instruction form) to you in connection with the solicitation of proxies by our Board for our 2021 annual meeting of stockholders. Due to the public health impact of the COVID-19 pandemic and to protect the health and well-being of our stockholders and other stakeholders, our annual meeting will be held at Two Newton Place, 255 Washington Street, Suite 100, Newton, Massachusetts 02458virtually via live webcast on Thursday, May 17, 2018,Tuesday, June 8, 2021, at 9:30 a.m., Eastern time.

The mailing address of the Company's principal executive offices is 400 Centre Street, Newton, Massachusetts 02458. The Company commenced mailingtime, subject to itsany adjournments or postponements thereof (the "2021 Annual Meeting"). We are first making these proxy materials available to stockholders a Notice Regarding the Availability of Proxy Materials containing instructions on how to access the Company's Proxy Statement and its 2017 Annual Report on Form 10-K on or about March 22, 2018.

All properly executed written proxies, and all properly completed proxies submitted by telephone or internet, that are delivered pursuant to this solicitation will be voted at the 2018 Annual Meeting in accordance with the directions given in the proxy, unless the proxy is revoked prior to it being exercised at the meeting. These proxies also may be voted at any postponements or adjournments of the meeting.April 7, 2021.

Only owners of record of shares of common stock par value $0.01 per share, of the Company ("Common Shares") as of the close of business on February 23, 2018,March 24, 2021, the record date for the meeting (the "Record Date"),our 2021 Annual Meeting, are entitled to notice of, and to vote at, the meeting and at any postponements or adjournments of the meeting. Holders of Common Shares are entitled to one vote for each Common Share held on the Record Date.record date. Our Common Shares are listed on The Nasdaq Stock Market LLC (the "Nasdaq"). On February 23, 2018,March 24, 2021, there were approximately 50,524,42431,676,091 Common Shares issued and outstanding.

The mailing address of our principal executive office is 400 Centre Street, Newton, Massachusetts 02458.

4    2    FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement

QUESTIONSTable of Contents

CORPORATE GOVERNANCE PRINCIPLES AND ANSWERSBOARD MATTERS

Proxy Materials and Voting Information

The proxy materials forWe are currently governed by a seven member Board of Directors. Ensuring our Board is comprised of Directors who bring diverse viewpoints and perspectives, exhibit a variety of skills, professional experience and backgrounds and effectively represent the 2018 Annual Meeting include the Notice Regarding the Availabilitylong term interests of Proxy Materials, Notice of 2018 Annual Meeting, this Proxy Statement and the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2017 (the "Annual Report" and, together with the other materials, the "proxy materials"). If you request a paper copy of these materials, the proxy materials will also include a proxy card or voting instruction form.

A proxy statementstockholders is a document that the Securitiestop priority of our Board and Exchange Commission ("SEC") regulations require the Company to give you when it asks you to return a proxy designating individuals to vote on your behalf. A proxy is your legal designation of another person to vote the shares you own. That other person is called your proxy. We are asking you to designate the following three personsour Nominating and Governance Committee. In February 2020, our Board added Dr. Michael E. Wagner as your proxies for the 2018 Annual Meeting:an Independent Director and Jennifer B. Clark Secretary; Bruce J. Mackey Jr., Presidentas a Managing Director to expand and Chief Executive Officer;refresh our Board's composition for several reasons, including to increase the ratio of Independent Directors to Managing Directors and Adam D. Portnoy, Managing Director.to create more skill mix.

OUR BOARD BELIEVES THAT ITS MEMBERS SHOULD:

If your shares are registered directlyIn addition, our Board has determined that our Board, as a whole, should strive to have the right mix of characteristics and skills necessary to effectively perform its oversight responsibilities. Our Board believes that Directors with one or more of the following professional skills or experiences can assist in your name with the Company's registrar and transfer agent, Equiniti Trust Company (formerly known as Wells Fargo Shareowner Services), you are considered a stockholder of record of those shares. If you are a stockholder of record, you should receive only one notice or proxy card for all the Common Shares you hold in certificate form and in book entry form.meeting this goal:

If your shares are held in an account you own at a bank or brokerage or you hold shares through another nominee, you are considered the "beneficial owner" of those shares. If you are a beneficial owner, you will receive voting instruction information from the bank, broker or other nominee through which you own your Common Shares.

If you hold some shares of record and some shares beneficially, you should receive a notice or proxy card for all the Common Shares you hold of record and a separate voting instruction form for the shares from the bank, broker or other nominee through which you own Common Shares.

By Written Proxy. All stockholdersOur Nominating and Governance Committee and our Board consider the qualifications, characteristics and skills of record can submit voting instructions by written proxy card. If you are a stockholder of recordDirectors and receive a Notice Regarding the Availability of Proxy Materials, you may request a written proxy card by following the instructions includedDirector candidates individually and in the notice. If you are a beneficial owner, you may request a written proxy card or a voting instruction form from your bank, broker or other nominee. Proxies submitted by mail must be received by 11:59 p.m., Eastern time, on May 16, 2018 or, if the meeting is postponed or adjourned to a later date, by 11:59 p.m., Eastern time, on the day immediately preceding the datebroader context of the reconvened meeting.

By Telephone or Internet. All stockholders of record also can authorize a proxy to vote their shares by touchtone telephone by calling 1-800-690-6903, or through the internet atwww.proxyvote.com, using the procedures and instructions described in your Notice Regarding the Availability of Proxy Materials or proxy card. Beneficial owners may authorize a proxy by telephone or internet if their bank, broker or otherour Board's overall composition when evaluating potential nominees for election as Director.

FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement    53

nominee makes those methods available, in which case the bank, broker or nominee will include the instructions with the proxy voting materials. To authorize a proxy by telephone or internet, you will need the 16 digit control number provided on your Notice Regarding the AvailabilityTable of Proxy Materials, proxy card or voting instruction form. The telephone and internet proxy authorization procedures are designed to authenticate stockholder identities, to allow stockholders to vote their shares and to confirm that their instructions have been recorded properly. Proxies submitted by telephone or through the internet must be received by 11:59 p.m., Eastern time, on May 16, 2018 or, if the meeting is postponed or adjourned to a later date, by 11:59 p.m., Eastern time, on the day immediately preceding the date of the reconvened meeting.Contents

In Person. All stockholders of record may vote in person at the meeting. Beneficial owners may vote in person at the meeting if they have a legal proxy, as described in the response toquestion 15.

Holders of record of Common Shares as of the close of business on February 23, 2018, the Record Date, may vote at the meeting. Holders of Common Shares are entitled to one vote for each Common Share held on the Record Date.

If you returnOur Board is elected by our stockholders to oversee our business and long term strategy. As part of fulfilling its responsibilities, our Board oversees the safeguarding of our assets, the maintenance of appropriate financial and other internal controls and our compliance with applicable laws and regulations. Inherent in these responsibilities is our Board's understanding and oversight of the various risks we face. Our Board considers that risks should not be viewed in isolation and should be considered in virtually every business decision and as part of our business strategy.

Our Board oversees risk as part of its general oversight of our Company. Oversight of risk is addressed as part of various Board and Board committee activities and through regular and special Board and Board committee meetings. Our day to day business is conducted by management, and management is responsible for incorporating risk management in its activities. Our Director of Internal Audit reports to our Audit Committee and provides us with advice and assistance with our risk management function.

In discharging their oversight responsibilities, our Board and Board committees review regularly a signed proxy card or authorize a proxywide range of reports provided to them by internet or telephonemanagement, internal audit and do not specify a choice for a matter, you will be instructing your proxy to vote in the manner recommended by the Board on that matter:service providers, including:

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FOR the election of both Director nominees identified in this Proxy Statement;reports on market and industry conditions;



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FORreports on the ratificationimpact of the appointmentCOVID-19 pandemic on our business, including cases of RSM US LLP as independent auditors.infections and administration of vaccinations;



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operating and regulatory compliance reports;



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reports on clinical operations;



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financial reports;



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reports on risk management activities;



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regulatory and legislative updates that may impact us;



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reports on the security of our information technology processes and our data; and



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legal proceedings updates and reports on other business related matters.

6    4    FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement

Table of Contents

Our Board and Board committees discuss these matters among themselves and with our management, our Director of Internal Audit, legal counsel, our independent auditors and other professionals, as appropriate.

Our Audit Committee takes a leading role in helping our Board fulfill its responsibilities for oversight of our financial reporting, internal audit function, risk management, including cybersecurity, and our compliance with legal and regulatory requirements. Our Board and Audit Committee review periodic reports from our independent auditors regarding potential risks, including risks related to our internal control over financial reporting. Our Audit Committee also reviews, approves and oversees an internal audit plan developed by our Director of Internal Audit with the goal of helping us systematically evaluate the effectiveness of our risk management, control and governance processes on an annual basis. Our Audit Committee meets at least quarterly and reports its findings to our Board. Our Audit Committee also meets periodically with our Director of Internal Audit to review the results of our internal audits, and directs or recommends to our Board actions or changes it determines appropriate to enhance or improve the effectiveness of our risk management.

Our Audit Committee considers risks related to cybersecurity and receives regular reports from our management regarding cybersecurity risks and countermeasures being undertaken or considered by us, including updates on the internal and external cybersecurity landscape and relevant technical developments.

Our Quality of Care Committee reviews management reports on our clinical operations and directs or recommends to management and our Board actions or changes it determines appropriate to improve our clinical operations and to reduce risks arising from those operations.

Our Compensation Committee whose duties are detailed in its charter, among other duties, evaluates the performance of our Director of Internal Audit and the performance of The RMR Group LLC ("RMR LLC") under our business management agreement. Also, our Compensation Committee and our Board consider that we have a share award program that requires share awards to executive officers to vest over a period of years. We believe that the use of share awards vesting over time rather than stock options mitigates the incentives for our management to undertake undue risks and encourages management to make long term and appropriately risk balanced decisions.

It is not possible to identify all of the risks that may affect us or to develop processes and controls to eliminate all risks and their possible effects, and processes and controls employed to address risks may be limited in their effectiveness. Moreover, it is necessary for us to bear certain risks to achieve our objectives. As a result of the foregoing and other factors, our ability to manage risk is subject to substantial limitations.

To learn more about the risks we face, you can review the matters discussed in Part I, "Item 1A. Risk Factors" and "Warning Concerning Forward-Looking Statements" in our Annual Report to Stockholders for the fiscal year ended December 31, 2020 (the "Annual Report"). The risks described in our Annual Report are not the only risks we face. Additional risks and uncertainties not currently known or that may currently be deemed to be immaterial also may materially adversely affect our business, financial condition or results of operations in future periods.

If youUnder the corporate governance listing standards of the Nasdaq, to be considered independent:

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a director must not have a disqualifying relationship, as defined in the corporate governance section of the Nasdaq rules; and



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our Board must affirmatively determine that the director otherwise has no relationship which would interfere with the exercise of independent judgment in carrying out the responsibilities of a director. To facilitate the director independence assessment process, our Board has adopted written Governance Guidelines as described below.

FIVE STAR SENIOR LIVING INC. 2021 Proxy Statement    5

Table of Contents

Our Board is comprised of seven Directors, including five Independent Directors and two Managing Directors. Under our Bylaws, so long as the number of directors is less than five, at least one director must meet the qualifications of a Managing Director and, so long as the number of directors is five or greater, at least two directors must meet the qualifications of a Managing Director. Our Bylaws require that a majority of our Board be Independent Directors. Under our Bylaws, Independent Directors are a beneficial ownerDirectors who are not employees of the Company or RMR LLC, are not involved in the Company's day to day activities and doare persons who qualify as an independent director under the applicable rules of the Nasdaq and the SEC. As set forth in our Bylaws, Managing Directors are Directors who are not provide voting instructions to your bank, broker or other nominee, the following applies:

Non-Discretionary Items. The election ofIndependent Directors is a non-discretionary item and may not be voted on by brokers, banks or other nominees who have not received specific voting instructions from beneficial owners. The resultbeen employees, officers or directors of the inabilityCompany or RMR LLC or involved in the day to day activities of the Company for at least one year prior to such Director's election.

Our Board affirmatively determines whether Directors have a broker, bankdirect or indirect material relationship with us, including our subsidiaries, other nomineethan serving as our Directors or trustees or directors of our subsidiaries. In making independence determinations, our Board observes the Nasdaq and SEC criteria, as well as the criteria set forth in our governing documents. When assessing a Director's relationship with us, our Board considers all relevant facts and circumstances, not merely from the Director's standpoint, but also from that of the persons or organizations with which the Director has an affiliation. Based on this review, our Board has determined that Barbara D. Gilmore, Donna D. Fraiche, Bruce M. Gans, M.D., Gerard M. Martin and Michael E. Wagner, M.D. currently qualify as independent directors under applicable Nasdaq and SEC criteria and as Independent Directors under our Bylaws. In making these independence determinations, our Board reviewed and discussed additional information provided by us and our Directors with regard to vote on a non-discretionary item foreach of the Directors' relationships with us, RMR LLC or The RMR Group Inc. ("RMR Inc."), the managing member of RMR LLC, and the other companies to which itRMR LLC or its subsidiaries provide management services. Our Board has not received specific voting instructions from beneficial owners is referred toconcluded that none of these five Directors possessed or currently possesses any relationship that could impair his or her judgment in connection with his or her duties and responsibilities as a broker non-vote.Director or that could otherwise be a direct or indirect material relationship under applicable Nasdaq and SEC standards.

Discretionary Items. The ratification of the appointment of RSM US LLP as independent auditors is a discretionary item. Generally, banks, brokers and other nominees that do not receive voting instructions from beneficial owners may vote on this proposal in their discretion.

A quorumPursuant to our Governance Guidelines, our Independent Directors are expected to meet at least twice per year in regularly scheduled meetings at which only Independent Directors are present. Our Independent Directors also meet separately with our officers, with our Director of stockholders is requiredInternal Audit and with our independent auditors. The presiding Director for stockholders to take action atpurposes of leading Independent Director sessions will be the 2018 Annual Meeting. The presence, in person or by proxy, of stockholders entitled to cast one-third of allLead Independent Director, unless the votes entitled to be cast at the 2018 Annual Meeting constitutes a quorum.Independent Directors determine otherwise.

Abstentions and broker non-votes are included in determining whether a quorum is present. Abstentions are not votes cast and, therefore, will not be included in vote totals and will have no effect on the outcome of any Item to be voted on at the 2018 Annual Meeting. A proxy marked "WITHHOLD" with respect to Item 1 will have the same effect as an abstention. Broker non-votes are not votes cast and, therefore, will not be included in vote totals and will have no effect on the outcome of Item 1. There can be no broker non-votes on Item 2 as it is a matter on which, if you hold your shares in street name and do not provide voting instructions to the broker, bank or other nominee that holds your shares, the nominee has discretionary authority to vote on your behalf.

StockholdersAll Directors play an active role in overseeing our business both at our Board and committee levels. As set forth in our Governance Guidelines, the core responsibility of our Directors is to exercise sound, informed and independent business judgment in overseeing our Company and our strategic direction. Our Directors are skilled and experienced leaders and currently serve or have the rightserved as members of senior management in public and private for profit and nonprofit organizations, including with healthcare related entities, and also have served in academia. Our Directors may be called upon to revoke a proxyprovide solutions to various complex issues and are expected to, and do, ask hard questions of our officers and advisers. Our Board is small, which facilitates informal discussions and communication from management to our Board and among Directors.

Adam D. Portnoy has served as Chair of our Board since 2019. One or more of our executive officers and our Director of Internal Audit, none of whom are members of our Board, regularly attend Board and Board committee meetings. Special meetings of our Board may be called at any time before itby the President, any Managing Director or any two Directors. Our Managing Directors, in consultation with our management and our Director of Internal Audit, set the agenda for Board meetings. Other Directors may suggest

Our Board has an Audit Committee, Compensation Committee, Nominating and Governance Committee and Quality of Care Committee. Our Audit Committee, Compensation Committee, Nominating and Governance Committee and Quality of Care Committee each have adopted a later date by internet or by telephone (only the last internet or telephone proxy submitted prior to the meeting will be counted) or by signingwritten charter, and returning a later dated proxy card or by attending the meeting and voting in person. If you are a beneficial owner, see the response toquestion 15.

A stockholder's attendance at the 2018 Annual Meeting will not revoke that stockholder's proxy unless that stockholder votes again at the meeting or sends an original written statement to the Secretary of the Company revoking the prior proxy. An original written notice of revocation or subsequent proxy should be delivered to Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458, Attention: Secretary, or hand delivered to the Secretary before the taking of the vote at the 2018 Annual Meeting.

Beneficial owners who wish to change their votes should contact the organization that holds their shares.each

FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement    7

The Notice of 2018 Annual Meeting, this Proxy Statement and the Annual Report are available atwww.proxyvote.com. You may access these proxy materials on the internet through the conclusion of the 2018 Annual Meeting.

Instead of receiving future copies of the Company's proxy materials by mail, stockholders of record and most beneficial owners may elect to receive these materials electronically. Opting to receive your future proxy materials electronically will save us the cost of printing and mailing documents, and also will give you an electronic link to our proxy voting site. Your Notice Regarding the Availability of Proxy Materials instructs you as to how you may request electronic delivery of future proxy materials.

The Company will report the final results in a Current Report on Form 8-K filed with the SEC following the completion of the 2018 Annual Meeting.

The Company bears all expenses incurred in connection with the solicitation of proxies. We will request banks, brokers and other nominees to forward proxy materials to the beneficial owners of Common Shares and to obtain their voting instructions. We will reimburse those firms for their expenses of forwarding proxy materials.

Proxies may also be solicited, without additional compensation, by the Company's Directors, officers and employees, and by The RMR Group LLC ("RMR LLC"), its officers and employees and its parent's and subsidiaries' directors, officers and employees, by mail, telephone or other electronic means or in person.

As permitted by the Securities Exchange Act of 1934, as amended (the "Exchange Act"), we may deliver only one copy of the Notice Regarding the Availability of Proxy Materials, Notice of 2018 Annual Meeting, this Proxy Statement and the Annual Report to Stockholders residing at the same address, unless the stockholders have notified us of their desire to receive multiple copies of those documents. This practice is known as "householding."

We will deliver a separate copy of any of those documents to you if you write to the Company at Investor Relations, Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458, or call the Company at (617) 796-8245. If you want to receive separate copies of our notices regarding the availability of proxy materials, notices of annual meetings, proxy statements and annual reports in the future, or if you are receiving multiple copies and would like to receive only one copy per household, you should contact your bank, broker or other nominee, or you may contact us at the above address or telephone number.

8    FIVE STAR SENIOR LIVING INC. 2018 Proxy Statement7

2018 Annual Meeting InformationTable of Contents

Board committee reviews its written charter on an annual basis to consider whether any changes are required.

Our Audit Committee, Compensation Committee, Nominating and Governance Committee and Quality of Care Committee are each comprised entirely of Independent Directors under applicable Nasdaq rules who also meet the independence criteria applicable to audit committees under the Sarbanes Oxley Act and the SEC's implementing rules under that law.

Our corporate governance materials are available for review in the governance section of our website, including our Governance Guidelines, the charter for each Board committee, the Code and information about how to report concerns or complaints about accounting, internal accounting controls or auditing matters and any violations or possible violations of the Code and how to communicate with our Directors, individually or as a group. To access these documents on our website, visit www.fivestarseniorliving.com.

All attendees need to bring photo identification for admission. Please note that cameras and audio or video recorders are not permitted at the meeting. Any cell phones, pagers or similar electronic devices must be shut off for the duration of the meeting.

Attendance at the meeting is limited to the Company's Directors and officers, stockholders as of the Record Date (February 23, 2018) or their duly authorized representatives or proxies, and other persons permitted by the Chairman of the meeting.

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Record owners: If you are a stockholder as of the Record Date who holds shares directly, you need not present any documentation to attend the 2018 Annual Meeting, other than photo identification.



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Beneficial owners: If you are a stockholder as of the Record Date who holds shares indirectly through a brokerage firm, bank or other nominee, you may be required to present evidence of your beneficial ownership of shares. For this purpose, a letter or account statement from the applicable brokerage firm, bank or other nominee confirming such ownership will be acceptable. Please note that you will not be able to vote your shares at the meeting without a legal proxy, as described in the response toquestion 15.



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Authorized named representatives: If you are a stockholder as of the Record Date and intend to appoint an authorized named representative to attend the meeting on your behalf, including if you are a corporation, partnership, limited liability company or other entity, you must notify us of your intent by regular mail to our Secretary or by email to secretary@5ssl.com.Requests for authorized named representatives to attend the meeting must be received no later than Thursday, May 10, 2018, or if the meeting is postponed or adjourned to a later date, on or before the 5^th business day before the reconvened meeting.

Please include the following information when submitting your request:

(1)

Your name and complete mailing address;

(2)

Proof that you owned shares of the Company as of February 23, 2018 (such as a copy of the portion of your voting instruction form showing your name and address, a bank or brokerage firm account statement or a letter from the bank, broker or other nominee holding your shares); and

(3)

A signed authorization appointing such individual to be your authorized named representative at the meeting, which includes the name, address, telephone number and email address of the authorized named representative.

Upon receipt of proper documentation, you and your named representative will receive confirmation that your named representative has been authorized to attend the meeting. For admission to the meeting, the photo ID presented must match the documentation provided in response to item (3) above. The Company reserves the right to limit the number of representatives who may attend the meeting.

If you have questions regarding these admission procedures, please call Investor Relations at (617) 796-8245.

FIVE STAR SENIOR LIVING INC. 2018 Proxy Statement    9

If you are a beneficial owner and want to vote your shares at the 2018 Annual Meeting, you need a legal proxy from your bank, broker or other nominee. You also need to follow the procedures described in the response toquestion 14 and to bring the legal proxy with you to the meeting and hand it in with a signed ballot that will be provided to you at the meeting. You will not be able to vote your shares at the meeting without a legal proxy. If you do not have a legal proxy, you can still attend the meeting by following the procedures described in the response toquestion 14. However, you will not be able to vote your shares at the meeting without a legal proxy. The Company encourages you to vote your shares in advance, even if you intend to attend the meeting.

Company Documents, Communications and Stockholder Proposals

You can visit our website to view our Governance Guidelines, Board committee charters and Code of Business Conduct and Ethics (the "Code"). To view these documents, go towww.fivestarseniorliving.com, click on "Investor Relations" and then click on "Corporate Governance." To view the Company's SEC filings and Forms 3, 4 and 5 filed by the Company's Directors and executive officers, go towww.fivestarseniorliving.com, click on "Investor Relations" and then click on "Financial Information & SEC Filings."

We will deliver free of charge, upon request, a copy of the Company's Governance Guidelines, Board committee charters, Code or Annual Report to any stockholder requesting a copy. Requests should be directed to Investor Relations at Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458.

Any stockholder or other interested person who wants to communicate with the Company's Directors, individually or as a group, should write to the party for whom the communication is intended, c/o Secretary, Five Star Senior Living Inc., 400 Centre Street, Newton, Massachusetts 02458 or email secretary@5ssl.com. The communication will then be delivered to the appropriate party or parties.

A proposal for action to be presented by any stockholder at the Company's 2019 annual meeting of stockholders must be submitted as follows:

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For a proposal to be eligible to be included in the proxy statement pursuant to Rule 14a-8 under the Exchange Act, the proposal must be received at the Company's principal executive offices by November 22, 2018.

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If the proposal is not to be included in the proxy statement pursuant to Rule 14a-8, the proposal must be made in accordance with the procedures and requirements set forth in our Amended and Restated Bylaws (our "Bylaws") and must be received by the Company not later than 5:00 p.m., Eastern time, on November 22, 2018 and not earlier than October 23, 2018.

Proposals should be sent to the Company's Secretary at Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458.

For additional information regarding how to submit a stockholder proposal, see page 34 of this Proxy Statement.

10    FIVE STAR SENIOR LIVING INC. 2018 Proxy Statement

ELECTION OF DIRECTORS (ITEM 1)

The Board serves as the decision making body of the Company, except for those matters reserved to the stockholders. The Board selects and oversees the Company's officers, who are charged by the Board with conducting the day to day business of the Company.

In accordance with our Articles of Amendment and Restatement (our "Charter") and our Bylaws, the Board currently consists of five Directors, three of whom are Independent Directors and two of whom are Managing Directors. Our Charter provides that the Board is divided into three groups, with Directors of each group serving for a term that expires at the third annual meeting of stockholders following his or her election and until his or her successor is elected and qualifies. In accordance with our Charter and Bylaws, on March 20, 2018, pursuant to a recommendation of the Nominating and Governance Committee, the Board elected Adam D. Portnoy as a Managing Director in Group I to fill the vacancy created by the death of Barry M. Portnoy on February 25, 2018 and to serve the remainder of the full term of the Group I Directors, the Group of Directors which stands for election at the 2020 annual meeting of shareholders.

Assuming a quorum is present at the meeting, a plurality of all the votes cast is required to elect a Director at the 2018 Annual Meeting.

The Nominating and Governance Committee is responsible for identifying and evaluating nominees for Director and for recommending to theour Board nominees for election at each annual meeting of stockholders. TheOur Nominating and Governance Committee may consider candidates suggested by the Company'sour Directors, officers or stockholders or by others.

Stockholder Recommendations for Nominees. Stockholders who would like to recommend a Director nominee for the position of Director should submit their recommendations in writing by mail to the Chair of theour Nominating and Governance Committee, c/o Five Star Senior Living Inc., Secretary, at Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458 or by email to secretary@5ssl.com. A stockholder'sAny such recommendation should include any information thata description of the recommendingcandidate's qualifications for Board service, the candidate's written consent to be considered for nomination and to serve if nominated and elected, as well as the addresses and telephone numbers for contacting the stockholder believes relevant toand the Nominating and Governance Committee's consideration. Thecandidate for more information. Our Nominating and Governance Committee may request additional information about the stockholder recommended nominee or about the stockholder recommending the nominee. Recommendations by stockholders will be considered by theour Nominating and Governance Committee in its discretion using the same criteria as other candidates it considers.

Our Board has established a process to facilitate communication by stockholders and other stakeholders with our Directors. Communications should be addressed to Directors in care of the Secretary, Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458 or by email to secretary@5ssl.com.

We understand the importance of leading a sustainable business and regularly consider ways to improve our internal culture and the communities in which we operate. Our environmental sustainability and community engagement strategies focus on a complementary set of objectives, including the following:

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Embrace Our Communities: We recognize the importance of aligning ourselves with the communities where we operate our senior living communities. We seek to be a responsible corporate citizen and to strengthen the communities in which we own or operate our senior living

Directors are responsible for overseeingother stockholder proposals, may be obtained by writing to our Secretary at Five Star Senior Living Inc., Two Newton Place, 255 Washington Street, Suite 300, Newton, Massachusetts 02458, or from the Company's business. This significant responsibility requires highly skilled individualsSEC's website, www.sec.gov. Any stockholder considering making a nomination or proposal should carefully review and comply with various qualities, attributes and professional experience. The Board believes that there are general requirements that are applicable to all Directors, qualifications applicable tothose provisions.

FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement    119

Independent Directors and other skills and experience that should be represented onTable of Contents

PROPOSAL 1: ELECTION OF DIRECTORS

Upon the Board as a whole, but not necessarily by each Director. In accordance withrecommendation of our Charter and Bylaws, the Board currently consists of five Directors: two Managing Directors and three Independent Directors. As set forth in our Bylaws, Independent Directors are Directors who are not employees of the Company or RMR LLC, who are not involved in the Company's day to day activities and who meet the qualifications of independent directors under the applicable rules of The Nasdaq Stock Market LLC (the "Nasdaq") and the SEC. As set forth in our Bylaws, Managing Directors are Directors who have been employees, officers or directors of the Company or RMR LLC or who have been involved in the Company's day to day activities for at least one year prior to their election as Directors. The Board and the Nominating and Governance Committee, consider the qualifications of Directors and Director candidates individually and in the broader context of the Board's overall composition and the Company's current and future needs.

Qualifications for All Directors

In its assessment of each potential candidate, including those recommended by stockholders, the Nominating and Governance Committee considers the potential nominee's integrity, experience, achievements, judgment, intelligence, competence, personal character, likelihood that a candidate will be able to serve on the Board for an extended period and other matters that the Nominating and Governance Committee deems appropriate. The Nominating and Governance Committee also takes into account the ability of a potential nominee to devote the time and effort necessary to fulfill his or her responsibilities to the Company.

The Board and Nominating and Governance Committee require that each Director candidate be a person of high integrity with a proven record of success in his or her field. Each Director candidate must demonstrate the ability to make independent analytical inquiries, familiarity with and respect for corporate governance requirements and practices and a commitment to serving the Company's long term best interests. In addition, the Nominating and Governance Committee may conduct interviews of potential Director candidates to assess intangible qualities, including the individual's ability to ask appropriate questions and to work collegially. The Board does not have a specific diversity policy in connection with the selection of nominees for Director, but due consideration is given to the Board's overall balance of diversity of perspectives, backgrounds and experiences.

In addition to other criteria, our Bylaws require that Director candidates submit any additional information required in connection with the Company's regulation by state healthcare regulatory authorities.

12    FIVE STAR SENIOR LIVING INC. 2018 Proxy Statement

Specific Qualifications, Attributes, Skills and Experience to be Represented on the Board

The Board has identified particular qualifications, attributes, skills and experience that are important to be represented on the Board as a whole, in light of the Company's long term interests. The following table summarizes certain key characteristics of the Company's business and the associated qualifications, attributes, skills and experience that the Board believes should be represented on the Board.

FIVE STAR SENIOR LIVING INC. 2018 Proxy Statement    13

The following table sets forth the names of the Director nominees and those Directors who will continue to serve after the 2018 Annual Meeting:

Upon the recommendation of the Nominating and Governance Committee, the Board has nominated Ms. Donna D. Fraiche and Gerard M. Martin, each for election as an Independent Director in Group II and Mr. Gerard M. Martin for election as a Managing Director in Group II.Director. Each Director nominee currently serves on theour Board. If elected, each nomineeof Ms. Fraiche and Mr. Martin would serve until the Company's 2021our 2024 annual meeting of stockholders and until his, her or hertheir successor is duly elected and qualifies, or until his or hersubject to the individual's earlier death, resignation, retirement, disqualification or removal.

We expect that each nominee for election as a Director will be able to serve if elected. However, if a nominee should become unable or unwilling to serve, proxies may be voted for the election of a substitute nominee designated by theour Board.

A plurality of all the votes cast is required to elect a Director at our 2021 Annual Meeting.

The Board believes that the combination of the various qualifications, attributes, skillsnames, principal occupations and experiences ofcertain other information regarding the Director nominees, would contribute to an effective Board serving the Company's long term best interests. The Board and the Nominating and Governance Committee believe that the Director nominees possess the necessary qualifications to provide effective oversight of the business and quality advice and counsel to the Company's management. Below isas well as a summary of the key experiences, qualifications, attributes, skills and skillsbackgrounds that led theour Nominating and Governance Committee and theour Board to conclude eachthat such person ispersons are currently qualified to serve as a Director.Directors, are set forth on the following pages.

TheOur Board of Directors recommends a vote "FOR" the election of both Director nominees.

14    10    FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement

Table of Contents

The following is some important biographical information, including the ages and recent principal occupations, as of March 20, 2018, of the Company's Directors, Director nominees and executive officers. The business address of the Directors, Director nominees and executive officers is c/o Five Star Senior Living Inc., 400 Centre Street, Newton, Massachusetts 02458. Included in each Director's biography below are the attributes of that Director consistent with the qualifications, attributes, skills and experience the Board has determined are important to be represented on the Board. For a general discussion of the particular Director qualifications, attributes, skills and experience, and the process for selecting and nominating individuals for election to serve as a Director, please see "Election of Directors" beginning on page 11.

Director Nominees

Donna D. Fraiche

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Donna D. Fraiche Independent Director since 2010 Lead Independent Director since 2019 Group/Term: Group II with a term expiring at the 2018our 2021 Annual Meeting Age: 6669

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Board Committees: Audit; Compensation; • Audit • Compensation • Nominating and Governance (Chair); • Quality of Care

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Other RMR Managed Public Company Boards(1): • Service Properties Trust (since 2015) • Office Properties Income Trust (since 2019) Other Non-RMR Managed Public Company Boards: Select Income REIT (since 2012); Hospitality Properties Trust (since 2015)None

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Ms. Fraiche is a member and the founder of Fraiche Strategies, LLC since 2020. Ms. Fraiche was senior counsel in the law firm of Baker, Donelson, Bearman, Caldwell & Berkowitz, PC and has practiced law in that firm since 2004.from 2004 to February 2020. Previously, Ms. Fraiche practiced law with the firm now known as Locke Lord LLP in New Orleans. Ms. Fraiche served as an independent trustee of Select Income REIT from 2012 until it merged with a wholly owned subsidiary of Office Properties Income Trust in December 2018. Ms. Fraiche is currently president of the Louisiana Chapter of the International Women's Forum and is the president of the Louisiana State Supreme Court Historical Society. She was appointed to the American Hospital Association Leadership Development Committee of the Committee on Governance for the term beginning in January 2017 and is a past president and a fellow of the American Health Lawyer'sLaw Association. She is a former chair of the Louisiana Health Care Commission and has previously served as chair of the Long Term Community Planning Task Force and Health Care Committee of the Louisiana Recovery Authority, delegate of the Louisiana Recovery Authority to the Louisiana Health Care Redesign Collaborative, and past chair of the board of trustees of Loyola University, among numerous other business and civic responsibilities. She serves on the executive board and on the investments committee of the Baton Rouge Area Foundation and served as chair of the board, on the executive committee, finance committee and real estate committee of Women's Hospital. Ms. Fraiche also serves as honorary consul generalHonorary Consul for Japan in New Orleans.

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Specific Qualifications, Attributes, Skills and Experience: • extensiveExtensive experience in, and knowledge of, the healthcare industry; • professionalProfessional legal skills; • manyMany leadership roles and experiences, including her service in numerous public policy and civic leadership roles; • workWork on public company boards and board committees; • institutionalInstitutional knowledge earned through prior service on theour Board; • Identifies Caucasian and as female; and • qualifyingQualifying as an Independent Director in accordance with the requirements of the Nasdaq, the SEC and our Bylaws.

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FIVE STAR SENIOR LIVING INC. 2018 Proxy Statement    15

Gerard M. Martin

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ManagingGerard M. Martin Independent Director since 20012020 Group/Term: Group II with a term expiring at the 2018our 2021 Annual Meeting Age: 8386

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Board Committees: • Audit • Nominating and Governance • Quality of Care

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Other RMR Managed Public Company Boards(1): None Other Non-RMR Managed Public Company Boards: None

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Prior to February 2020, Mr. Martin served as a Managing Director. Mr. Martin was the founder and chairman of Greenery Rehabilitation Group, Inc., a company in the business of owning and operating nursing homes and health rehabilitation facilities, which was publicly owned and first listed on the Nasdaq and then the New York Stock Exchange between 1985 and 1993. Mr. Martin is the owner and treasurer of North Atlantic Medical Services, Inc., a private company in the business of providing diagnostic cardiac, respiratory and oxygen services, equipment and products for the care of patients in their homes or medical facilities. Mr. Martin served as a director and vice president of RMR Advisors LLC, an SEC registered investment adviser, from 2002 to 2015, and a director of RMR LLC and its predecessors from 1986 to 2015. Mr. Martin was also an interested trustee of the RMR Funds Series Trust theand RMR Real Estate Income FundMortgage Trust and its predecessor funds from shortly after their formation (the earliest of which was in 2002) until 2009.

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Specific Qualifications, Attributes, Skills and Experience: • extensiveExtensive experience in, and knowledge of, the healthcare industry; • experienceExperience as an operator of nursing and rehabilitation facilities; • extensiveExtensive public company director service; • institutionalInstitutional knowledge earned through prior service on theour Board since the Company's formation and in leadership positions with RMR LLC; and • qualifyingIdentifies as a ManagingCaucasian and as male; and • Qualifying as an Independent Director in accordance with the requirements of the Nasdaq, the SEC and our Bylaws.Bylaws

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(1)

In addition to our Company, RMR LLC or its subsidiaries currently provide management services to seven other public companies, including the following six public companies that do not have any employees of their own: Diversified Healthcare Trust (Nasdaq: DHC) Industrial Logistics Properties Trust (Nasdaq: ILPT), Office Properties Income Trust (Nasdaq: OPI), Service Properties Trust (Nasdaq: SVC), Tremont Mortgage Trust (Nasdaq: TRMT) and RMR Mortgage Trust (Nasdaq: RMRM). For these companies with no employees, RMR LLC or its subsidiaries provide all business operations and functions pursuant to the terms of the applicable business management agreements. RMR LLC also provides business management services to one other public operating company, TravelCenters of America Inc. (Nasdaq: TA), which has its own employees but some members of the senior leadership of this company are also RMR LLC employees.

16    FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement11

DirectorsTable of Contents

Bruce M. Gans, M.D.

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Bruce M. Gans, M.D. Independent Director since 2001 Group/Term: Group III with a term expiring at the 2019our 2022 annual meeting of stockholders Age: 7174

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Board Committees: Audit; • Audit • Compensation (Chair); • Nominating and Governance; Governance • Quality of Care (Chair)

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Other RMR Managed Public Company Boards:Boards(1): • Industrial Logistics Properties Trust (since 2017)2018) Other Non-RMR Managed Public Company Boards: None

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Dr. Gans has beenserved as executive vice president and chief medical officer at the Kessler Institute for Rehabilitation sincefrom 2001 until his retirement on March 31, 2021 and national medical director for Rehabilitation Select Medical, the parent company of the Kessler Institute, since 2003.from 2003 until his retirement on March 31, 2021. He is also a professor of physical medicine and rehabilitation at Rutgers University—New Jersey Medical School. Dr. Gans was an independent trustee of HospitalityService Properties Trust from 2009 until 2015. Dr. Gans has also served as president and chief executive officer of the Rehabilitation Institute of Michigan. In Dr. Gans's extensive academic career, he has served as professor of physical medicine and rehabilitation at a number of universities, in addition to his current position at Rutgers University—New Jersey Medical School. Dr. Gans is editor of a standard medical textbook on physical medicine and rehabilitation, which is now in its fifth edition, and he has written or coauthored more than forty articles in peer-reviewed publications and twenty-eight abstracts and has served on editorial boards for many medical journals, including serving as the associate editor of the American Journal of Physical Medicine and Rehabilitation. Dr. Gans has testified before the Senate Committee on Veterans' Affairs and has been called on to serve on technical expert panels and to advise the Medicare Payment Advisory Commission, the independent congressional agency established in 1997 to advise the U.S. Congress on issues affecting the Medicare program. Dr. Gans has also served as president of the American Academy of Physical Medicine and Rehabilitation, a medical society with more than 7,500 members, and as a leader in numerous other professional organizations.

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Specific Qualifications, Attributes, Skills and Experience: • demonstratedDemonstrated leadership capability, including through his service in many healthcare management, professional, academic and civic leadership positions; • businessBusiness experience as the chief executive of a large medical organization; • extensiveExtensive experience in, and knowledge of, the healthcare industry and healthcare public policy matters; • workWork on public company boards and board committees; • manyMany academic and professional achievements; • institutionalInstitutional knowledge earned through prior service on the Board since the Company's formation; andour Board; • qualifyingIdentifies as Caucasian and as male; and • Qualifying as an Independent Director in accordance with the requirements of the Nasdaq, the SEC and our Bylaws.

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Jennifer B. Clark Managing Director since 2020 Group/Term: Group III with a term expiring at our 2022 annual meeting of stockholders Age: 59

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Other RMR Managed Public Company Boards(1): • The RMR Group Inc. (since 2018) • Diversified Healthcare Trust (since 2018) Other Non-RMR Managed Public Company Boards: None

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Ms. Clark has been executive vice president, general counsel and secretary of RMR Inc. since shortly after its formation in 2015. Ms. Clark joined RMR LLC in 1999 as a vice president; she became a senior vice president in 2006, an executive vice president and general counsel in 2008 and secretary in 2015. Ms. Clark also serves as an officer of ABP Trust, a director and secretary of Sonesta Holdco Corporation and executive vice president, general counsel and secretary of Tremont Realty Advisors LLC. Ms. Clark serves as the secretary of each of the companies to which RMR LLC or its subsidiaries provide management services, including the Company and Diversified Healthcare Trust. Ms. Clark also served as a trustee of RMR Mortgage Trust from 2019 to January 2021 and secretary of RMR Office Property Fund LP from 2018 until its dissolution in July 2020. Ms. Clark also served as a director of RMR Advisors LLC from 2016 to 2021 when it merged with Tremont Realty Advisors LLC, as its president and chief executive officer from 2019 to 2021, and prior to that as its executive vice president and general counsel from October 2017 through December 2018 and as its secretary from 2004 to 2021, and as vice president and chief legal officer from 2007 through September 2017. Prior to joining RMR LLC, Ms. Clark was a partner at the law firm of Sullivan & Worcester LLP.

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Specific Qualifications, Attributes, Skills and Experience: • Professional skills and experience in legal, corporate governance and real estate matters; • Leadership position with RMR LLC and demonstrated management ability; • Extensive experience in, and knowledge of, the commercial real estate industry and real estate investment trusts ("REITs"); • Institutional knowledge earned through prior service as an officer of the Company and in leadership positions with RMR LLC; • Identifies as Caucasian and as female; and • Qualifying as a Managing Director in accordance with the requirements of our Bylaws.

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12    FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement    17

Table of Contents

Barbara D. Gilmore

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Michael E. Wagner, M.D. Independent Director since 2020 Group/Term: Group III with a term expiring at our 2022 annual meeting of stockholders Age: 61

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Dr. Wagner has served as chief physician executive of Wellforce, a Massachusetts healthcare system since May 2018. He served as interim president and chief executive officer of Wellforce during 2019. He is also an associate professor of clinical medicine at Tufts University School of Medicine. Prior to joining Wellforce, Dr. Wagner held a number of positions with one of its founding members, Tufts Medical Center, including president and chief executive officer from 2013 to 2018, president and chief executive officer of Tufts Medical Center Physicians Organization from 2012 to 2014, chief medical officer from 2011 to 2013, and chief, internal medicine and adult primary care from 2008 to 2012. While at Tufts Medical Center, Dr. Wagner also served on its board of trustees and was a member of many of its committees, including the compensation, governance and nominating, finance, audit, investment and real estate and quality of care committees at various times from 2011 to 2018. Prior to joining Tufts, Dr. Wagner held various positions in health care organizations and hospitals.

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Specific Qualifications, Attributes, Skills and Experience: • Professional skills and experience in healthcare industry • Demonstrated leadership capability, including through his service in many healthcare management, professional and academic positions; • Business experience as the chief executive of a large medical organization; • Extensive experience in, and knowledge of, the healthcare industry and healthcare public policy matters; • Identifies as Caucasian and as male; and • Qualifying as an Independent Director in accordance with the requirements of the Nasdaq, the SEC and our Bylaws.

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Barbara D. Gilmore Independent Director since 2004 Group/Term: Group I with a term expiring at the 2020our 2023 annual meeting of stockholders Age: 6770

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Other RMR Managed Public Company Boards:Boards(1): • TravelCenters of America LLCInc. (since 2007); Government • Office Properties Income Trust (since 2009) • RMR Mortgage Trust (formerly known as RMR Real Estate Income Fund, since 2020) Other Non-RMR Managed Public Company Boards: None

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Ms. Gilmore has served as a professional law clerk at the United States Bankruptcy Court, Eastern Division of the District of Massachusetts, sincefrom 2015 until her retirement in 2018, and prior to that, at the United States Bankruptcy Court, Central Division of the District of Massachusetts, from 2001 to 2015. Ms. Gilmore was a partner of the law firm of Sullivan & Worcester LLP from 1993 to 2000, during which time she was appointed and served as trustee or examiner in various cases involving business finance matters. Ms. Gilmore was also a registered nurse and practiced and taught nursing for several years before attending law school and her practice at Sullivan & Worcester LLP included representation of businesses in the healthcare sector.

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Specific Qualifications, Attributes, Skills and Experience: • experienceExperience in, and knowledge of, the healthcare industry; • professionalProfessional skills and experience in legal, business finance and healthcare regulatory matters and nursing; • experienceExperience as a lawyer, bankruptcy court clerk, bankruptcy trustee and bankruptcy examiner; • workExperience in public policy matters; • Insights gained and understanding of government practices through government service; • Work on public company boards and board committees; • institutionalInstitutional knowledge earned through prior service on theour Board; • Identifies as Caucasian and as female; and • qualifyingQualifying as an Independent Director in accordance with the requirements of the Nasdaq, the SEC and our Bylaws.

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18    FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement13

Adam D. PortnoyTable of Contents

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Adam D. Portnoy Managing Director since 2018 Chair of our Board since 2019 Group/Term: Group I with a term expiring at the 2020our 2023 annual meeting of stockholders Age: 4750

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Other RMR Managed Public Company Boards(1): • Other Public Company Boards: HospitalityService Properties Trust (since 2007); Senior Housing Properties • Diversified Healthcare Trust (since 2007); Government • Office Properties Income Trust (since 2009); • RMR Mortgage Trust (formerly known as RMR Real Estate Income Fund, including its predecessor funds (sincesince 2009); Select Income REIT (since 2011); • The RMR Group Inc. (since 2015); • Industrial Logistics Properties Trust (since 2017); • Tremont Mortgage Trust (since 2017); • TravelCenters of America LLCInc. (since 2018) Other Non-RMR Managed Public Company Boards: None

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Mr. Portnoy has been a managing director of The RMR Group Inc. ("RMR Inc.") and its president and chief executive officer of RMR Inc. since shortly after its formation in 2015. Mr. Portnoy has been president and chief executive officer of RMR LLC since 2005 and was a director of RMR LLC from 2006 until June 5, 2015 when RMR LLC became a majority owned subsidiary of RMR Inc. and RMR Inc. became RMR LLC's managing member. Mr. Portnoy has beenis the sole trustee and controlling shareholder and an officer of ABP Trust. Mr. Portnoy is a director and controlling shareholder of RMR Advisors LLC since 2007 and served as its president from 2007 to September 2017 and its chief executive officer from 2015 to September 2017.Sonesta Holdco Corporation. Mr. Portnoy has been a director of Tremont Realty Advisors LLC since March 2016, and he wasserved as its president and chief executive officer from March 2016 through December 2017. Mr. Portnoy is an owner and has beenserved as a director of Sonesta International Hotels Corporation since 2012.RMR Advisors LLC from 2007 to 2021 when it merged with Tremont Realty Advisors LLC and served as its president from 2007 to 2017 and its chief executive officer from 2015 to 2017. Mr. Portnoy served as president and chief executive officer of RMR Real Estate Income FundMortgage Trust from 2007 to 2015 and as president of GovernmentOffice Properties Income Trust from 2009 to 2011. Mr. Portnoy was a managing trustee of Equity Commonwealth from 2006 until 2014 and served as its presidentSelect Income REIT from 2011 to 2014.until it merged with a wholly owned subsidiary of Office Properties Income Trust in December 2018. Prior to joining RMR LLC in 2003, Mr. Portnoy held various positions in the finance industry and public sector, including working as an investment banker at Donaldson, Lufkin & Jenrette and ABN AMRO as well as working in private equity at DLJ Merchant Banking Partners and at the International Finance Corporation (a member of The World Bank Group). In addition, Mr. Portnoy previously founded and served as chief executive officer of a privately financed telecommunications company. Mr. Portnoy currently serves as the honorary consul generalHonorary Consul General of the Republic of Bulgaria into Massachusetts and as chair of the board of directors of the Pioneer Institute and as a member AJC New England's Leadership Board, and previously served on the board of governors for the National Association of Real Estate Investment Trusts and the board of trustees of Occidental College.

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Specific Qualifications, Attributes, Skills and Experience: • extensiveExtensive experience in, and knowledge of, the CRE industry;commercial real estate industry and REITs; • leadershipLeadership position with RMR LLC and demonstrated management ability; • knowledge of the Company's businessesPublic company trustee and industries;director service; • public company director service; • experienceExperience in investment banking and private equity; • experienceExperience in starting a telecommunications company and serving as its senior executive; • institutionalInstitutional knowledge earned through prior service on our Board and in leadership positions with RMR LLC; and • qualifyingIdentifies as Caucasian and as male; and • Qualifying as a Managing Director in accordance with the requirements of our Bylaws. Our Nominating and Governance Committee and our Board believe that, because Mr. Portnoy is the president and chief executive officer of RMR LLC and the business of all the companies (including our Company) for which he serves as a managing trustee or managing director is integral to his day to day work, his service on these additional boards does not impair the amount of attention or time that Mr. Portnoy spends on service on our Board. Our Board believes that Mr. Portnoy's extensive familiarity with our day to day business provides valuable insight for our Board.

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14    FIVE STAR SENIOR LIVING INC.     20182021 Proxy Statement    19

Executive Officers

Bruce J. Mackey Jr.Table of Contents

The Company's executive officers serve at the discretion of our Board. There are no family relationships among any of the Company's Directors or executive officers.

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Katherine E. Potter Age: 45

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President and Chief Executive Officer since 20082019

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Age: 47 Mr. MackeyMs. Potter previously served as the Company's Chief Financial OfficerExecutive Vice President and TreasurerGeneral Counsel in 2018, as Senior Vice President and General Counsel from 2001 until 2008. Mr. Mackey2016 to 2018 and as Vice President and General Counsel from 2012 to 2016. Ms. Potter has been an executive vice president of RMR LLC since 2011, a senior vice president of RMR LLC from 2006 to 2011 and was vice president of RMR LLC from 2001 to 2006. Prior to 2001, he served in various capacities for RMR LLC and its affiliates. Mr. Mackey is a certified public accountant.

Richard A. Doyle, Jr.

						Chief Financial Officer and Treasurer since 2016 Age: 49 Mr. Doyle previously served as chief financial officer and treasurer of SNH from 2007 through 2015. He previously served as the Company's Director of Financial Reporting from 2005 to 2006. Prior to that, Mr. Doyle was employed by Sun Life Financial in positions involving finance and accounting for 10 years. He has also been employed as a senior vice president of RMR LLC since 2007 and an employee of RMR LLC since 2006. Mr. Doyle holds an MBA degree and is a certified public accountant.

R. Scott Herzig

						Senior Vice President and Chief Operating Officer since 2012 Age: 49 Mr. Herzig previously served as the Divisional Vice President of the Company's Western Division from 2007 to 2012,2018 and prior to that served as onea vice president of the Company's regional directors of operationsRMR LLC from 20002016 to 2007.

Katherine E. Potter

Senior Vice President and General Counsel since 2016 Age: 42 Ms. Potter previously served as Vice President and General Counsel of the Company from 2012 to 2016. Prior to joining the Company,2018. Ms. Potter practiced law in private practice for over ten years, focusing on corporate, securities, mergers and acquisitions, corporate governance and other transactional matters. Ms. Potter was an associate at the law firm of Sullivan & Worcester LLP from 2005 to 2011, and she was an attorney at the law firm of Burns & Levinson LLP from 2011 to 2012. Ms. Potter identifies as Caucasian and as female.

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Jeffrey C. Leer Age: 41

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Executive Vice President, Chief Financial Officer and Treasurer since 2019

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Mr. Leer has served as senior vice president of RMR LLC since June 2019. Previously, Mr. Leer served as the chief financial officer and treasurer of Office Properties Income Trust from January 2019 to May 2019 and chief financial officer and treasurer of Select Income REIT until December 2018 when it merged with a wholly owned subsidiary of Office Properties Income Trust. Mr. Leer has also held various positions with RMR LLC since 2013. Prior to joining RMR LLC, Mr. Leer held accounting and finance positions at several Fortune 500 companies, including having served as a reporting and compliance manager of Boston Scientific Corporation from June 2012 to February 2013, and practiced for several years in public accounting. Mr. Leer is a certified public accountant. Mr. Leer identifies as Caucasian and as male.

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