Bertioga is a Brazilian municipality of the state of São Paulo in the Baixada Santista. The population in 2004 was 35,759. However, because it neighbors resort towns, its population fluctuates greatly with the seasons. The population density is 72.68/km² and it has an area of 492 km² (190 sq mi) The more northern parts are dense forests and are virtually unpopulated. The municipality was created in 1995. Prior to that it was considered a suburb of Guaruja.
Its limits are Mogi das Cruzes, Biritiba-Mirim and Salesópolis in the north, São Sebastião in the east, Atlantic Ocean to the south with ilha de Santo Amaro (opposite to the city) and Santos in the west.