Mad River Township is one of the twelve townships of Champaign County, Ohio, United States.

Located in the southwestern part of the county, it borders the following townships: No municipalities are located in Mad River Township, although the unincorporated communities of Thackery and Westville lie in the township's southwest and northeast respectively.

The other townships of this name are located in Clark and Montgomery counties.

The township is governed by a three-member board of trustees, who are elected in November of odd-numbered years to a four-year term beginning on the following January 1.

There is also an elected township fiscal officer,[5] who serves a four-year term beginning on April 1 of the year after the election, which is held in November of the year before the presidential election.