São Sebastião (Portuguese for Saint Sebastian) is a Brazilian municipality, located on the southeast coast of Brazil, in the state of São Paulo. The population in 2009 was 76,344, its density was 182.5/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.