Mandeville Island is an island in the Sacramento–San Joaquin Delta located about 15 miles (24 km) northwest of Stockton, in central California in the United States. The island covers about 5,500 acres (2,200 ha), and lies between the Old River to the west and Middle River to the east, both distributaries of the San Joaquin River-Stockton Deepwater Shipping Channel. The forms the island's southern end, and borders the island to the north. The island lies directly to the east of Franks Tract State Recreation Area. It is in San Joaquin County, and managed by Reclamation District 2027.