UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

Current Report

Pursuant to Section 13 or 15(d) of The

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): March 14, 2014

UNUM GROUP

(Exact name of registrant as specified in its charter)

1 Fountain Square

Chattanooga, Tennessee 37402

(Address of principal executive offices) (Zip Code)

(423) 294-1011

(Registrant’s telephone number, including area code)

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Item 8.01 Other Events.

On March 14, 2014, Unum Group, a Delaware corporation (“Unum Group” or the “Company”), announced that it had completed an offering of $350,000,000 aggregate principal amount of 4.000% Senior Notes due 2024 (the “Notes”). The Notes were offered and sold pursuant to an Underwriting Agreement, dated March 11, 2014 (the “Underwriting Agreement”), and issued by the Company under an Indenture dated as of August 23, 2012. Copies of the Underwriting Agreement, the form of the Notes, the opinion of Sullivan & Cromwell LLP, special counsel to the Company, relating to the validity of the Notes, and a news release concerning the offering of Notes are attached hereto as Exhibits 1.1, 4.1, 5.1 and 99.1, respectively.

The Notes were offered and sold under the Company’s effective registration statement on Form S-3 (File No. 333-177892) filed with the U.S. Securities and Exchange Commission (the “SEC”) on November 10, 2011. The Company has filed with the SEC a prospectus supplement, dated March 11, 2014, together with the accompanying base prospectus, dated November 10, 2011, relating to the offer and sale of the Notes.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits. The following exhibits are filed with this report:

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

INDEX TO EXHIBITS