The Treaty of Asunción was a treaty between the countries of Argentina, Brazil, Paraguay, and Uruguay signed on March 26, 1991. The objective of the treaty, signed in Asunción, was to establish a common market among the participating countries, popularly called Mercosur (Southern Common Market). Later, the Treaty of Ouro Preto was signed to supplement the first treaty, establishing that the Treaty of Asunción was to be a legally and internationally recognized organization.