Located in the central part of the county, it borders the following townships: Parts of two municipalities are located in Greenfield Township: the city of Lancaster, the county seat of Fairfield County, in the southeast; and the village of Carroll in the northwest.

Greenfield Township was established in 1805, and named for the green fields within its borders.

[4] Statewide, other Greenfield Townships are located in Gallia and Huron 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.