San Esteban Island (Spanish: Isla San Esteban, Seri: Coftéecöl [koɸˈtɛːkʷɬ] and sometimes Hast [ʔast]) 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 Sea of Cortés.