San Andrés (island) is a coral island among the Colombian islands in the Caribbean Sea; it is the largest island of the southern group of islands with 26 km2. Together with the nearby island of Providencia and some smaller islands of the southern group of the Colombian archipelago, San Andrés forms part of the department of San Andres, Providencia and Santa Catalina. The island's location in South America has been aptly described as "Geographically near Nicaragua, historically tied to England, and politically part of Colombia since 1802.

While San Andres island is located 50 km (31 mi) to the north of Providencia, the Colombian archipelago is approximately 775 km (470 mi) from the Colombian main land and about 199 km (140 mi) east of Nicaragua.

This archipelago encompass a total area of 57 km2 (22 sq mi), including the outer cays, reefs, atolls and sand banks with 45 km2 (17 sq mi) being the area of the islands. In 2000, it was declared a UNESCO Biosphere Reserve, named “Sea flower Biosphere Reserve”, which not only includes the islands but also about 10% of the Caribbean Sea, amounting to a vast marine area of 300,000 km2 (120,000 sq mi).[The purpose of this declaration is to ensure that the ecosystem which has a large biodiversity is well preserved and conserved.