Table of Contents

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 11-K

FOR ANNUAL REPORTS OF EMPLOYEE STOCK PURCHASE, SAVINGS AND

SIMILAR PLANS PURSUANT TO SECTION 15(d) OF THE SECURITIES

EXCHANGE ACT OF 1934

ANNUAL REPORT PURSUANT TO SECTION 15(d) OF

THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2016

F.N.B. Corporation Progress Savings 401(k) Plan

F.N.B. Corporation

12 Federal Street

One North Shore Center

Pittsburgh, PA 15212

Table of Contents

AUDITED FINANCIAL STATEMENTS AND

SUPPLEMENTAL SCHEDULE

F.N.B. Corporation Progress Savings 401(k) Plan

Years Ended December 31, 2016 and 2015

With Report of Independent Registered Public Accounting Firm

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Audited Financial Statements

and Supplemental Schedule

Years Ended December 31, 2016 and 2015

Contents

Table of Contents

Report of Independent Registered Public Accounting Firm

Plan Administrator and Participants

F.N.B. Corporation Progress Savings 401(k) Plan

We have audited the accompanying statements of net assets available for benefits of the F.N.B. Corporation Progress Savings 401(k) Plan (the “Plan”) as of December 31, 2016 and 2015, and the related statement of changes in net assets available for benefits for the years then ended. These financial statements are the responsibility of the Plan’s management. Our responsibility is to express an opinion on these financial statements based on our audits.

We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 2016 and 2015, and the changes in net assets available for benefits for the years then ended, in conformity with accounting principles generally accepted in the United States of America.

The supplemental information in the accompanying Schedule H, Line 4(i) - Schedule of Assets (Held at End of Year) as of December 31, 2016 has been subjected to audit procedures performed in conjunction with the audit of F.N.B. Corporation Progress Savings 401(k) Plan’s financial statements. The supplemental information is presented for the purpose of additional analysis and is not a required part of the financial statements but include supplemental information required by the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. The supplemental information is the responsibility of the Plan’s management. Our audit procedures included determining whether the supplemental information reconciles to the financial statements or the underlying accounting and other records, as applicable, and performing procedures to test the completeness and accuracy of the information presented in the supplemental information. In forming our opinion on the supplemental information in the accompanying schedule, we evaluated whether the supplemental information, including its form and content, is presented in conformity with the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. In our opinion, the supplemental information in the accompanying schedule is fairly stated in all material respects in relation to the financial statements as a whole.

/s/ Baker Tilly Virchow Krause, LLP

Pittsburgh, Pennsylvania

June 16, 2017

1

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Statements of Net Assets Available for Benefits

December 31, 2016 and 2015

See accompanying notes to financial statements.

2

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Statements of Changes in Net Assets Available for Benefits

Years ended December 31, 2016 and 2015

See accompanying notes to financial statements.

3

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements

December 31, 2016 and 2015

1. Description of Plan

The following description of the F.N.B. Corporation Progress Savings 401(k) Plan (the Plan) provides only general information. Participants should refer to the summary plan description for a more complete description of the Plan’s provisions.

General

The Plan is a qualified 401(k) defined contribution plan, covering all eligible employees of F.N.B. Corporation (the Corporation), including the following subsidiaries: First National Bank of Pennsylvania; Regency Finance Company; First National Trust Company; First National Investment Services Company, LLC; F.N.B. Investment Advisors, Inc.; First National Insurance Agency, LLC; and Bank Capital Services LLC. The Plan is subject to the provisions of the Employee Retirement Income Security Act of 1974 (ERISA).

All non-temporary employees are eligible to participate in the Plan. An eligible employee may enroll in the Plan the day following the date the employee commences employment. An eligible employee who does not enroll in the Plan will be automatically enrolled in the Plan following 30 days of employment, unless the employee opts out of the Plan before then.

In March 2017, the Corporation completed a merger with Yadkin Financial Corporation (“Yadkin”). In connection with the merger employees who were active participants in the defined contribution plan sponsored by Yadkin were permitted to immediately participate in the Plan.

4

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

1. Description of Plan (continued)

Contributions

Participants may contribute up to 50% of their pre-tax annual compensation. An eligible employee who is automatically enrolled in the Plan will be deemed to have elected to have 3% (2% prior to April 2016) of his or her compensation contributed on a pre-tax basis to the Plan. Participants who have attained age 50 by the end of the plan year are eligible to make catch-up contributions. Participants may also contribute amounts representing distributions from other qualified plans (rollovers). Participants direct the investment of their vested contributions into various investment options offered by the Plan.

The Corporation matched 100% of a participant’s elective pre-tax contribution, up to 6% of the participant’s compensation in 2016 and 2015. The Plan also provides for a discretionary performance-based contribution determined annually by the Corporation. The discretionary performance-based contribution to the Plan can be up to 3% of a participant’s compensation, based on the extent to which the Corporation achieved its performance goals for the year. The discretionary performance-based contribution will only be made on behalf of eligible participants who are employed by the Corporation on the last day of the Plan year, or retire during the Plan year and meet various other conditions. Discretionary performance-based contributions amounted to 0.066% and 0.31% of eligible compensation for 2016 and 2015 or $122,281 and $488,211, respectively.

Matching contributions and performance-based contributions are made in the form of either shares of F.N.B Corporation common stock or cash used to acquire shares of F.N.B. Corporation common stock.

T. Rowe Price Trust Company (TRP) is the appointed trustee for all Plan assets.

5

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

1. Description of Plan (continued)

Dividends on F.N.B. Corporation Common Stock

Dividends on F.N.B. Corporation common stock are automatically reinvested in the Plan for all participants. However, participants may make a special request to receive a cash distribution of dividend payments on F.N.B. Corporation common stock.

Participant Accounts

Each participant’s account is credited with their voluntary contribution and the Corporation’s matching and performance-based contributions, and an allocation of the Plan’s net earnings, as defined by the Plan. The voluntary contribution and employer match is paid semi-monthly at the end of each payroll period. The performance-based contributions, if any, are paid within 90 days after the end of the plan year.

Vesting

Participants are immediately vested in their voluntary contribution, Corporation’s matching contribution, and cash dividends paid on F.N.B. Corporation common stock, plus actual earnings thereon. Participants are 100% vested in the Corporation’s performance-based contributions and actual earnings thereon after three years of service.

Participants become 100% vested when attaining the age of 65 or in the event of death or permanent disability.

Forfeitures

Upon a participant’s separation from service, the non-vested portion of the participant’s account will be forfeited upon the earlier of the date the participant receives an account distribution or the date the participant incurs a five-year break in service. Forfeited amounts are used to reduce the Plan’s administrative expenses or to reduce future Corporation contributions. The ending forfeiture balance at December 31, 2016 and 2015 totaled $12,955 and $11,352, respectively. During the plan year, forfeitures of $650 and $80,000 were used to reduce Corporation contributions for 2016 and 2015, respectively. Forfeitures of $82,500 and $81,242 were used to reduce administrative expenses for 2016 and 2015, respectively.

6

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

1. Description of Plan (continued)

Payment of Benefits

Upon separation of service, vested account balances of less than $1,000 will be paid in a single lump sum as soon as practicable after separation. Vested account balances greater than $1,000 will be distributed when requested by the participant.

The Plan permits withdrawals before separation of service under certain circumstances. Voluntary pre-tax contributions may be withdrawn provided the participant has an immediate and heavy financial need (as defined by the Internal Revenue Code) and other sources of funds, including plan loans, are not available. Also, after reaching age 59 and 1/2, participants may withdraw all or a portion of a vested account balance.

Notes Receivable from Participants

Notes receivable from participants are measured at their unpaid principal balance plus any accrued but unpaid interest.

Participants who remain actively employed by the Corporation may borrow from their accounts up to a maximum equal to the lesser of $50,000 or 50% of their vested account balance. Loan terms may not exceed five years, unless the participant uses the proceeds of the loan to acquire a principal residence, in which case the repayment period must be reasonable as determined by the Plan Administrator. Loans are secured by the balance in the participant’s account and bear an interest rate of prime plus 1%. Principal and interest are paid ratably through payroll deductions.

Plan Termination

Although it has not expressed any intent to do so, the Corporation has the right under the Plan to discontinue its contributions at any time and to terminate the Plan subject to the provisions of ERISA. In the event of plan termination, the participants will become 100% vested in their accounts.

7

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

2. Summary of Significant Accounting Policies

Basis of Presentation

The financial statements have been prepared on the accrual basis of accounting in accordance with accounting principles generally accepted in the United States of America.

Investment Valuation and Income Recognition

Investments held by a defined contribution plan are required to be carried at fair value. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. See Note 3 for a discussion of fair value measurements.

Dividend income is recorded on the ex-dividend date. Interest income from other investments is recorded as earned on an accrual basis.

Purchases and sales of securities are recorded on a trade-date basis.

8

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

2. Summary of Significant Accounting Policies (continued)

Administrative Expenses

Certain administrative expenses of the Plan are paid by the Corporation. Such expenses have historically been comprised of fees of audit, custody and recordkeeping services and have been insignificant in relation to the Corporation and the Plan. Administrative expenses paid by the Corporation on behalf of the Plan totaled $38,111 and $45,167 for plan years 2016 and 2015, respectively.

Contributions

Participant contributions are recorded in the month withheld from participants’ wages. Corporation matching contributions are paid and recorded in the same month as participant contributions. Other annual Corporation contributions are generally made within 90 days following the plan year end.

Distributions to Participants

Distributions to participants are recorded when paid by the trustee.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.

Risks and Uncertainties

The Plan invests in various investments. These investments are exposed to various risks such as interest rate, market, liquidity and credit risks. Due to the level of risk associated with certain investments and the sensitivity of certain fair value estimates to changes in valuation assumptions, it is at least reasonably possible that changes in the values of investments will occur in the near term and that such changes could materially affect participants’ account balances and the amounts reported in the statements of net assets available for benefits.

As of December 31, 2016 and 2015, the Plan had two investments, including an investment in the Corporation’s common stock further described in Note 5, in the amount of $87,404,767 and $73,670,394, respectively.

9

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

3. Fair Value Measurements

The Fair Value Measurement topic of the FASB Accounting Standards Codification (Topic 820) provides the framework for measuring fair value. That framework provides for a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (level 1) and the lowest priority to unobservable inputs (level 3). The three levels of the fair value hierarchy are described as follows:

The asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Valuation techniques used must maximize the use of observable inputs and minimize the use of unobservable inputs.

10

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

3. Fair Value Measurements (continued)

Following is a description of the valuation methodologies used for investments measured at fair value. There have been no changes in the valuation methodologies used during 2016 and 2015.

F.N.B. Corporation common stock: The common stock of the Corporation is traded on a national exchange and is valued using last trading price on the last business day of the plan year.

Mutual funds: Shares of mutual funds are valued at the net asset value (NAV) of shares held by the Plan at year end, based upon published market quotations on national exchanges.

Common collective trust fund: The common collective trust fund is valued at the NAV of units of a bank collective trust. The NAV, as provided by the trustee, is used as a practical expedient to estimate fair value. The NAV is based on the fair value of the underlying investments held by the fund less its liabilities. This practical expedient is not used when it is determined to be probable that the fund will sell the investments for an amount different than the reported NAV. Participant transactions (purchases and sales) may occur daily. Were the Plan to initiate a full redemption of the collective trust, the investment adviser reserves the right to temporarily delay withdrawal from the trust in order to ensure that securities liquidations will be carried out in an orderly business manner.

The preceding methods described may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, although the Plan believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain instruments could result in a different fair value measurement at the reporting date.

11

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

3. Fair Value Measurements (continued)

The following tables set forth by level within the fair value hierarchy the Plan’s investments at fair value as of December 31, 2016:

The following tables set forth by level within the fair value hierarchy the Plan’s investments at fair value as of December 31, 2015:

The fair value of the employer contributions receivable approximates the carrying value based upon its short-term nature.

(a) In accordance with Topic 820, certain investments that were measured at net asset value per share (or its equivalent) have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the line items presented in the statements of net assets available for benefits.

12

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

3. Fair Value Measurements (continued)

The following table summarizes investments for which fair value is measured using NAV per share practical expedient as of December 31, 2016 and 2015, respectively. There are no participant redemption restrictions for these investments; the redemption notice period is applicable only to the Plan.

13

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

4. Income Tax Status

The Plan received a determination letter from the Internal Revenue Service dated September 24, 2013, stating that the Plan is qualified under Section 401(a) of the Internal Revenue Code (the Code) and, therefore, the related trust is exempt from taxation. Subsequent to this determination by the Internal Revenue Service, the Plan was amended. Once qualified, the Plan is required to operate in conformity with the Code to maintain its qualification. The Plan Administrator believes the Plan is being operated in compliance with the applicable requirements of the Code and, therefore, believes that the Plan is qualified and the related trust is tax-exempt.

Accounting principles generally accepted in the United States of America require plan management to evaluate tax positions taken by the Plan. The Plan Administrator has analyzed the tax positions taken by the Plan, and has concluded that as of December 31, 2016 and 2015 there are no uncertain tax positions taken or expected to be taken that would require recognition of a liability (or asset) or disclosure in the financial statements. The Plan is subject to routine audits by taxing authorities; however, there are currently no audits for any tax years in progress. The Plan Administrator believes it is no longer subject to income tax examinations for years prior to 2013.

5. Parties-in-Interest Transactions

Certain plan investments are interests in a common collective trust (Stable Value Common Trust Fund) issued by T. Rowe Price Trust Company (T. Rowe Price) and certain mutual funds managed by T. Rowe Price. T. Rowe Price is the trustee as defined by the Plan and, therefore, these transactions qualify as party-in-interest transactions. Fees paid to T. Rowe Price for administration services were $102,419 and $78,562 during 2016 and 2015, respectively. Additionally, an affiliate of the Corporation provides certain investment advisory services to the Plan. Fees paid related to these services were $82,500 during 2016 and 2015. Additionally, certain administrative functions of the Plan are performed by officers or employees of the Corporation. No such officer or employee receives compensation from the Plan.

One of the investment options in the Plan is F.N.B. Corporation common stock. At December 31, 2016 and 2015, the Plan held an aggregate of 4,057,353 and 4,035,442 shares of F.N.B. Corporation common stock valued at $65,039,373 and $53,832,803, respectively. Dividends received on F.N.B. Corporation common stock were $1,984,737 and $1,855,039 for 2016 and 2015, respectively. During 2016, the Plan purchased 1,212,644 shares of F.N.B. Corporation Stock at an aggregate cost of $12.2 million and sold 1,137,779 shares of F.N.B. common stock for proceeds of $12.5 million. The Plan distributed 52,954 in-kind shares of F.N.B. Corporation stock in 2016. During 2015, the Plan purchased 1,393,370 shares of F.N.B. Corporation Stock at an aggregate cost of $15.5 million and sold 935,260 shares of F.N.B. common stock for proceeds of $10.1 million. The Plan distributed 42,527 in-kind shares of F.N.B. Corporation stock in 2015. Notes receivable from participants are also considered party-in-interest transactions.

14

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

Notes to Financial Statements (continued)

December 31, 2016 and 2015

6. Reconciliation of Financial Statements to Form 5500

The following is a reconciliation of the change in net assets available for benefits per the financial statements to the net income reported in Form 5500:

15

Table of Contents

Supplemental Schedule

16

Table of Contents

F.N.B. Corporation

Progress Savings 401(k) Plan

EIN #25-1255406         Plan #002

Schedule H, Line 4(i) – Schedule of Assets

(Held at End of Year)

December 31, 2016

17

Table of Contents

EXHIBITS

18

Table of Contents

SIGNATURES

The Plan. Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees (or other persons who administer the employee benefit plan) have duly caused this annual report to be signed on its behalf by the undersigned, thereunto duly authorized.

19