Osasco is a municipality in São Paulo State, Brazil, located in the Greater São Paulo area and ranking 5th in population among São Paulo municipalities. According to the IBGE 2015, Osasco currently has the 9th highest gross domestic product in Brazil, and the 2nd largest in the State of São Paulo. The population is 699,944 in an area of 64.95 km2. It is among the world's more dense cities, similar in density to Tokyo and New York City. It's considered the major urban centre of the Western portion of the Greater São Paulo. It used to be a district of São Paulo City until February 19, 1962, when Osasco became a municipality of its own. The city motto is "Urbs labor", a Latin phrase that means "City work".

Greater São Paulo is a nonspecific term for one of the multiple definitions of the large metropolitan area located in the São Paulo state in Brazil.