The 2020 census reported 5,520 people living in the township.

Located in the southwest corner of the county, it borders the following townships: The entire township lies in the Virginia Military District.

Most of the village of Blanchester is located in western Marion Township.

[5] [citation needed] 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,[6] 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.