SECOND SUPPLEMENTAL INDENTURE

Exhibit 4.1

EXECUTION VERSION

SECOND SUPPLEMENTAL INDENTURE

THIS SECOND SUPPLEMENTAL INDENTURE (this “Second Supplemental Indenture”) is dated as of August 16, 2016, by and among Huntington Bancshares Incorporated, a Maryland corporation (“Huntington”), FirstMerit Corporation, an Ohio corporation (“FirstMerit”) and Wells Fargo Bank, National Association, as trustee (the “Trustee”).

RECITALS

WHEREAS, FirstMerit and the Trustee entered into a Subordinated Indenture dated as of February 4, 2013 (the “Original Indenture”);

WHEREAS, on February 4, 2013, FirstMerit and the Trustee entered into that certain First Supplemental Indenture (the “First Supplemental Indenture”), pursuant to which FirstMerit issued $250 million of its 4.350% Subordinated Notes due 2023;

WHEREAS, on the date of this Second Supplemental Indenture, West Subsidiary Corporation, an Ohio corporation and a direct, wholly-owned subsidiary of Huntington, will merge with and into FirstMerit, with FirstMerit being the surviving corporation, and as reasonably as practicable thereafter, FirstMerit will merge with and into Huntington, with Huntington being the surviving corporation (the merger of FirstMerit into Huntington, the “Merger”), whereupon the separate corporate existence of FirstMerit will cease;

WHEREAS, Section 801 of the Original Indenture (as amended by the First Supplemental Indenture and this Second Supplemental Indenture, the “Indenture”) requires that Huntington expressly assume, by an indenture supplemental to the Original Indenture, executed and delivered by Huntington to the Trustee, in form satisfactory to the Trustee, the due and punctual payment of the principal of (and premium, if any) and interest on or any Additional Amounts in respect of all the Securities and the performance of every other covenant of the Indenture on the part of FirstMerit to be performed or observed;

WHEREAS, Section 901 of the Indenture authorizes, without the consent of any Holders of Securities, the execution of a supplemental indenture, in form satisfactory to the Trustee, to evidence the succession of another Person to FirstMerit, and the assumption by any such successor of the covenants and obligations of FirstMerit under the Indenture and the Securities;

WHEREAS, each of Huntington and FirstMerit desires the Trustee to join with it in the execution and delivery of this Second Supplemental Indenture and has delivered to the Trustee an Officer’s Certificate and an Opinion of Counsel satisfying the requirements of the Indenture;

WHEREAS, the execution and delivery of this Second Supplemental Indenture is authorized and permitted by the Original Indenture and the First Supplemental Indenture, and complies with the Trust Indenture Act; and

WHEREAS, capitalized terms used and not otherwise defined herein shall have the respective meanings assigned to such terms in the Indenture.

NOW, THEREFORE, in compliance with Section 901 of the Indenture, and in consideration of the covenants contained herein and intending to be legally bound hereby, Huntington, FirstMerit and the Trustee, for the benefit of each other and for the benefit of the Holders of Securities, agree as follows:

“Effective August 16, 2016, FirstMerit Corporation, an Ohio corporation (“FirstMerit”), was merged with and into Huntington Bancshares Incorporated, a Maryland corporation (“Huntington”), with Huntington as the surviving corporation. Pursuant to the Second Supplemental Indenture, dated as of August 16, 2016, Huntington assumed the obligations of FirstMerit and the performance of every covenant and condition of the Indenture and the Notes on the part of FirstMerit to be performed or observed.”

If Huntington shall so determine, new Securities so modified as to conform to the Indenture as hereby supplemented, in form satisfactory to the Trustee, may at any time hereafter be prepared and executed by Huntington and authenticated and delivered by the Trustee in accordance with Section 906 of the Indenture in exchange for the Securities then outstanding, and thereafter the notation herein provided shall no longer be required. Anything herein or in the Indenture to the contrary notwithstanding, the failure to affix the notation herein provided as to any Security or to exchange any Security for a new Security modified as herein provided shall not affect any of the rights of the holder of such Security. The CUSIP number for the Notes shall not be changed by the Merger.

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[Signature page follows]

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IN WITNESS WHEREOF, the parties hereto have caused this Second Supplemental Indenture to be duly executed by their respective officers thereunto duly authorized, as of the day and year first above written.

[Signature Page to Second Supplemental Indenture]