Ilha Grande is an island located off the coast of Rio de Janeiro state, Brazil. The island, which is part of the municipality of Angra dos Reis, remains largely undeveloped. For almost a century it was closed by the Brazilian government to free movement or settlement because it first housed a leper colony and then a top-security prison. Cândido Mendes high-security prison housed some of the most dangerous prisoners within the Brazilian penal system. It was closed in 1994. The largest village on the island is called Vila do Abraão with approximately 1900 inhabitants.
The island, which is 193 km² in area, is now a popular tourist destination that is noted for its scenic beauty, unspoilt tropical beaches, luxuriant vegetation and rugged landscape. The highest point is the 1,031 m Pico da Pedra D'Água. Most of its territory is within the Ilha Grande State Park. The remainder of the island is subject to stringent development restrictions.
On 5 July 2019, Ilha Grande and Paraty were inscribed as a UNESCO World Heritage Site.