Monhegan is a plantation in Lincoln County, Maine, United States, about off the mainland. The population was 75 at the 2000 census. The plantation comprises its namesake island and the uninhabited neighboring island of Manana. The island is accessible by mailboat ferry (no automobiles) from Boothbay Harbor, New Harbor and Port Clyde. It was designated a National Natural Landmark for its coastal and island flora in 1966.