St. George is a town in Knox County, Maine, United States. The population was 2,591 at the 2010 census. It includes the villages of Port Clyde, Clark Island, Glenmere, Martinsville and Tenants Harbor, the latter its commercial center. A favorite with artists, writers and naturalists, St. George is home to the Brothers and Hay Ledge nature preserve, comprising four islands off Port Clyde.