São Sebastião (Portuguese for Saint Sebastian) is a Brazilian city, located on the southeast coast of Brazil, in the state of São Paulo. The population in 2003 is 65,477, its density is 162.47/km² and the area is 403 km². The Tropic of Capricorn lies 25 km north. The municipality existed since 1636 and formed a part of the old hereditary captaincy of Santo Amaro. The urban area is on the Atlantic coast, much of the area are heavily forested to the north and makes up Serra do Mar with no accessible roads to the north.
The island of São Sebastião which is part of the municipality of Ilhabela is located in the west coast of São Sebastião. The coast is located in the commercial centre of the city. Between the city and the island is the São Sebastião canal with 30 kilometres in length, and variable width (7km being the shortest crossing).
The city is famous for its beaches and tourism. Beaches include (from north to south) Preta, Grande (or dos Trabalhadores), Pitangueiras, Cabelo Gordo, Barequeçaba, Guaecá, Brava de Guaecá, Toque-Toque Grande, Toque-Toque Pequeno, Calhetas, Santiago, Paúba, Maresias, Brava de Maresias, Boiçucanga, Camburi, Baleia, Barra do Sahy, Conchas, Juquehy, Barra do Una, Juréia, e Boracéia. Near the boundary with Bertioga there is a small Amerindian village.