Topsham is a town in Sagadahoc County, Maine, United States. Topsham was included in the Lewiston-Auburn, Maine metropolitan New England city and town area. The population was 9,560 at the 2020 census. It is part of the Portland–South Portland–Biddeford, Maine metropolitan statistical area. The town is home to the annual Topsham Fair.

Sagadahoc County is a county located in the U.S. state of Maine. As of the 2020 census, the population was 36,699. Its county seat is Bath. In geographic area, it is the smallest county in Maine.