The Pelotas Basin (Portuguese: Bacia de Pelotas, Spanish: Cuenca de Pelotas) is a mostly offshore sedimentary basin of approximately 346,000 square kilometres (134,000 sq mi) in the South Atlantic, administratively part of the southern states Santa Catarina and Rio Grande do Sul of Brazil and the departments Cerro Largo, Rocha and Treinta y Tres of Uruguay.