The inlet known as Long Reach nearly splits the island in two.
Sebascodegan Island or Great Island is an island at the eastern edge of Casco Bay on the Gulf of Maine. It is a part of the town of Harpswell with the mainland portion of Harpswell to its west and Orr's Island and Bailey Island to its south. The town of Brunswick occupies the mainland to the north, and the towns of West Bath and Phippsburg occupy the mainland to the east, across the New Meadows River.
Coordinates: 43°49′54″N 69°55′09″W / 43.83167°N 69.91917°W