Aransas Bay is a bay on the Texas Gulf Coast, approximately 30 miles (48 km) northeast of Corpus Christi, and 173 miles (278 km) south of San Antonio. It is separated from the Gulf of Mexico by San José Island (also referred to as St. Joseph Island). Aransas Pass is the most direct navigable outlet into the Gulf of Mexico from the bay. The cities of Aransas Pass and Port Aransas are located at the southern end, and Rockport is found on the central western shore. The bay is oriented laterally northeast-southwest, and is extended by Redfish Bay to the southwest, Copano Bay to the west, Saint Charles Bay to the north, and Mesquite Bay to the northeast. Aransas Bay is part of the Mission-Aransas National Estuarine Research Reserve.