Exhibit 5.1

Audrey Boone Tillman, Esq.

Executive Vice President and General Counsel

August 7, 2020

The Board of Directors

Aflac Incorporated

1932 Wynnton Road

Columbus, Georgia 31999

Ladies and Gentlemen:

As General Counsel of Aflac Incorporated, a Georgia corporation (the “Company”), I have represented the Company in connection with the preparation of a Registration Statement on Form S-3, which is being filed by the Company with the Securities and Exchange Commission (the “Commission”) on the date hereof (the Registration Statement”) relating to the registration and issuance by the Company of an aggregate of up to 9,000,000 shares (the “Shares”) of the common stock, par value $0.10 per share (the “Common Stock’), of the Company pursuant to the AFL Stock Plan: A Direct Stock Purchase and Dividend Reinvestment Plan (the “Plan”).

This opinion is delivered in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act of 1933, as amended (the “Securities Act”).

In connection with this opinion, I am familiar with the corporate proceedings taken by the Company in connection with the authorization of the Plan, and have made such other examinations of law and fact as considered necessary in order to form a basis for the opinion hereafter expressed.

I am admitted to the bar in the State of Georgia and I do not express any opinion with respect to the law of any other jurisdiction. The opinion expressed herein is based on laws in effect on the date hereof, which are subject to change with possible retroactive effect.

Based upon and subject to the foregoing, I am of the opinion that when the Shares have been delivered and paid for in accordance with the terms and conditions of the Plan, the issuance and sale of the Shares will have been duly authorized and, subject to any restrictions imposed by the Plan, the Shares will be validly issued, fully paid and nonassessable.

I hereby consent to the filing of this opinion with the Commission as Exhibit 5.1 to the Registration Statement.

Very truly yours,

/s/ Audrey Boone Tillman

Audrey Boone Tillman, Esq.