Lily Bay State Park, Public recreation area on Moosehead Lake in Greenville, United States.

Lily Bay State Park covers 924 acres (374 ha) on the southeast shore of Moosehead Lake, New England's largest lake, in Greenville, Piscataquis County. A two-mile trail follows the shoreline, used for hiking, snowshoeing and cross-country skiing. The park has camping, boating, fishing, swimming and snowmobiling.

Lily Bay State Park was established in 1961 on 924 acres of woodland mostly donated by the Scott Paper Company in 1959. In July 1962, Governor John H. Reed officially dedicated the park on the southeast shore of Moosehead Lake.

The park's name comes from the lily pads in the shallow bays of Moosehead Lake, where the two-mile shoreline trail passes campsites and swimming areas. Anglers fish these waters for brook trout and landlocked salmon, and in winter snowmobilers cross the park on groomed routes.

The park lies on the southeast shore of Moosehead Lake, reached from Greenville in Piscataquis County. A two-mile trail follows the lake shore and is used for hiking, snowshoeing and cross-country skiing. Camping, boating, fishing, swimming and snowmobiling are the activities the park is set up for.

Lily Bay State Park was one of five Maine state parks in the path of totality for the 2024 solar eclipse, where observers had 3 minutes and 14 seconds of darkness. The park's 924 acres lie on the southeast shore of Moosehead Lake, the largest lake in New England.