Barreta Island (Portuguese: Ilha da Barretta) is an island in Algarve, Portugal, about 7 kilometres (4.3 mi) long and 50 to 600 metres (160 to 1,970 ft) wide.

Barreta is also known as Deserta, Deserted Island or Santa Maria Cape Island. Is one of the more isolated islands in Algarve. There is a public ferry line reaching the island everyday, all year round or it can be reached by renting or owning a boat. In this island is located the southernmost point of continental Portugal, Cabo de Santa Maria.

A beach on the island is used by naturists.