international organization founded to promote the preservation of the Amazon (Amazon River) basin and regulate Amazonian development through international cooperation. The Amazon Cooperation Treaty was drafted and signed on July 3, 1978, by Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname, and Venezuela. In 1995 the countries formed ACTO to meet the goals outlined in the treaty. ACTO has four official languages: Dutch, English, Portuguese, and Spanish.

The countries of ACTO, believing that progressive improvement of Amazonian life hinges on the management of the Amazon basin, have created many programs and established agreements to sustain biodiversity and promote conservation and resource management in the Amazon. For example, Project GEF Amazonas, a program funded through the Global Environment Facility, has strived to achieve agreement on a renewable and integrated water supply, and the ACTO Biodiversity Program has promoted a healthy biological balance to prevent ecosystem fragmentation.

In 2004 ACTO was responsible for the Manaus Declaration, a treaty designed to coordinate the development of approximately 2.9 million square miles (7.5 million square km) of rainforest. The declaration reaffirmed the commitment of member countries to promote the social and economic development of the Amazon and the preservation of its cultures. ACTO also has created programs that allow groups of students to learn more about the Amazon and has sponsored mutually beneficial agreements with various indigenous communities.