Ohio Rev. Code § 3103.06: Contracts affecting marriage.

(A) A husband and wife may, by any contract with each other, do any of the following:

(1) Enter into a postnuptial agreement that alters their legal relations with each other;

(2) Modify or terminate an antenuptial or postnuptial agreement or any other agreement that alters their legal relations with each other;

(3) Agree to an immediate separation and make provisions for the division of property and support of either of them and their children during the separation.

(B) An agreement under division (A)(1) or (2) of this section shall comply with section 3103.061 of the Revised Code.