Lemesurier Island is the second-largest island in the Icy Strait between Chichagof Island and the mainland of the Alaska Panhandle in Alaska, USA. The island lies about midway between the mainland city of Gustavus and the northwest Chichagof Island community of Elfin Cove.
The island was named by George Vancouver, after William Le Mesurier (1767-1833), a midshipman on the HMS Chatham.
It has a land area of 27.534 km² ( 10.631 sq mi) and reported a population of one person in the 2000 census. Together with Pleasant Island and the Inian Islands, it forms the Pleasant/Lemesurier/Inian Islands Wilderness, a wilderness area within Tongass National Forest that has been officially designated by the National Wilderness Preservation System.