Newcastle is a town in Lincoln County, Maine, United States. The population was 1,848 at the 2020 census. The village of Newcastle is located in the eastern part of the town, on the Damariscotta River. Together with the village of Damariscotta linked by the Main Street bridge, they form the Twin Villages.

Lincoln County is a county located in the U.S. state of Maine. As of the 2020 census, the population was 35,237. Its seat is Wiscasset. The county was founded in 1760 by the Massachusetts General Court from a portion of York County, Massachusetts and named after the English city Lincoln, the birthplace of Massachusetts Bay Provincial Governor Thomas Pownall.