Sarstoon Island is an island at the southernmost point of Belize located near the mouth of the Sarstoon River. The main channel of Sarstoon River is located south of Sarstoon Island and forms part of the Belize–Guatemala border. Sarstoon Island is part of the Toledo District of Belize, which is one of 6 districts of the country. The island is mostly mangrove swampland and is uninhabited. It covers approximately 0.68 square kilometres (0.26 mi2).