Mogi Guaçu is a municipality in the state of São Paulo in Brazil. The population is 153,033 in an area of 813 km2. The city is at an average elevation of 591 m above sea level. Mogi Guaçu is a place name that probably originates from the Tupi language. It means "large river of snakes". The city was founded on April 9, 1877. The municipality contains the 469 hectares Mogi-Guaçu Biological Reserve, a fully protected conservation area created in 1942.