| Praia do Sul State Biological Reserve | |
| Alt Name: | Reserva Biológica Estadual da Praia do Sul |
| Iucn Category: | Ia |
| Map: | Brazil |
| Relief: | yes |
| Nearest City: | Angra dos Reis, Rio de Janeiro |
| Coordinates: | -23.176°N -44.288°W |
| Designation: | Biological reserve |
| Created: | 2 December 1981 |
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.The purpose was to preserve the natural ecosystems home to indigenous flora and fauna.It was integrated with the Aventureiro Marine State Park, created in 1990, which covers the shores and waters of the bay to the south of the reserve.It is within the Tamoios Environmental Protection Area, created in 1982.It is part of the Bocaina Mosaic, created in 2006.
On 28 May 2014 the area was reduced by 2.7% to accommodate the Vila do Aventureiro.The area is now about .The former marine state park and the small part of the biological reserve is now the Aventureiro Sustainable Development Reserve.A skeleton found in the reserve was dated to 3,000 years ago, and showed that he was a strong rower and expert diver.
As of 2009 the State Biological Reserve was a "strict nature reserve" under IUCN protected area category Ia, with a total area of .The reserve is open only for educational or research purposes.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.There is a rich variety of rainforest trees and large mangroves.Along with the Ilha Grande State Park about 87% of the island or are protected.