Penikese Island lies off the coast of Massachusetts, United States, in Buzzards Bay. It is part of the Elizabeth Islands, which form the town of Gosnold, Massachusetts. Penikese was originally home to the Anderson School of Natural History, a predecessor to the Marine Biological Laboratory in Woods Hole. It was only open two years, and was destroyed by fire in 1895. In 1904 Penikese became home to a leper colony, and today it houses a reform school.
The United States Census Bureau lumps Penikese along with the smaller nearby Gull Island to the east into Block 6043, Block Group 6, Census Tract 2004 of Dukes County, Massachusetts. The two islands together have a land area of 0.397 km² (98.2 acres) and no permanent population, even though Penikese Island houses a transient population at the Penikese Island School.