San Esteban Island (, Seri: Coftéecöl and sometimes Hast ) is a small island in the Gulf of California, Mexico, located to the southwest of Tiburón Island. It is part of the Municipality of Hermosillo in Sonora, and has a land area of 39.773 km² (15.356 sq mi), the 15th-largest island in Mexico. It is located in the Gulf of California. It was once inhabited by a group of the Seri people.