Newcastle is a census-designated place (CDP) comprising the main village of the town of Newcastle in Lincoln County, Maine, United States.

The CDP extends south down the river to a location north of Little Point, and north upriver and along Salt Bay to Damariscotta Mills and the outlet of Damariscotta Lake.

[3] US Route 1 passes through the community, leading northeast 26 miles (42 km) to Rockland and southwest 18 miles (29 km) to Bath.

U.S. Route 1 Business splits off US 1 to run through the centers of Newcastle and Damariscotta as Main Street.

Maine Route 215 has its southern terminus at US 1 Business in Newcastle and leads north 16 miles (26 km) to ME 32 in the northern part of the town of Jefferson.