Richmond is a town in Sagadahoc County, Maine, United States. The population was 3,522 at the 2020 census. It is part of the Portland–South Portland–Biddeford, Maine metropolitan statistical area, situated at the head of Merrymeeting Bay. Richmond is located adjacent to the 2,019 acre state-owned and managed Steve Powell Wildlife Management Area on Swan Island, a wildlife sanctuary and tourist area listed on the National Register of Historic Places.