Winthrop is located at (44.311812, −69.968699) [REF].
According to the United States Census Bureau, the CDP has a total area of 7.2 square miles (18.6 km²), of which, 5.6 square miles (14.4 km²) of it is land and 1.6 square miles (4.2 km²) of it (22.78%) is water.