Praia do Sul State Biological Reserve (Portuguese: Reserva Biológica Estadual da Praia do Sul) is a biological reserve on the island of Ilha Grande, in the State of Rio de Janeiro, in Brazil.

The reserve was created on 2 December 1981 on Praia do Sul, Ilha Grande, in the municipality of Angra dos Reis.

[2] It was integrated with the 1,312 hectares (3,240 acres) Aventureiro Marine State Park, created in 1990, which covers the shores and waters of the bay to the south of the reserve.

[6] A skeleton found in the reserve was dated to 3,000 years ago, and showed that he was a strong rower and expert diver.

[1] About half of the reserve is covered in dense Atlantic Forest, with many species of flora and fauna including parrots, otters, woodpeckers, shore birds, monkeys, armadillos, pacas and snakes.