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. San Esteban Island is home to many types of rare animal species found on only a few of the islands, such as the San Esteban chuckwalla (Sauromalus varius), the spiny chuckwalla (S. hispidus) and the spiny-tailed iguana (Ctenosaura conspicuosa).