Watertown Township is one of the twenty-two townships of Washington County, Ohio, United States.

The 2020 census found 1,541 people in the township.

Located in the northwestern part of the county, it borders the following townships: No municipalities are located in Watertown Township, although the unincorporated community of Watertown lies in the township's center.

[4] 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.