The South American Common Market, or Mercosur, is an economic and political agreement among Argentina, Brazil, Paraguay and Uruguay.

It was founded in 1991 by the Treaty of Asuncion, which was signed on March 26, 1991, in the capital city of Paraguay and amended by the 1994 Protocol of Ouro Preto.

It promotes free trade to allow the fluid movement of goods, people and currency. It officially started operation on Jan 1, 1995, and is now a full customs union.