Lyman is a town in York County, Maine, United States. The population was 4,525 at the 2020 census. It is part of the Portland–South Portland–Biddeford, Maine metropolitan statistical area. Lyman, together with Alfred, is home to Massabesic Experimental Forest.

York County is the southwesternmost county in the U.S. state of Maine, along the state of New Hampshire's eastern border. It is divided from Strafford County, New Hampshire, by the Salmon Falls River and the connected tidal estuary, the Piscataqua River. York County was permanently established in 1639. Several of Maine's earliest colonial settlements are found in the county, which is the state's oldest and one of the oldest in the United States. As of the 2020 census, its population was 211,972, making it Maine's second-most populous county. Its county seat is Alfred. York County is part of the Portland–South Portland, Maine Metropolitan Statistical Area.