Marcos Paz is the capital of Marcos Paz Partido, in the Greater Buenos Aires urban agglomeration in the Argentine province of Buenos Aires, located 48 kilometres west of Buenos Aires.
Although the city of Marcos Paz was officially founded in 1878, the city was first established in 1870, near the Estación Coronel Doctor Marcos Paz railway station. With a population of 39.529 (INDEC 2001), it is the county's largest (and only) city.