The Gran Chaco or Dry Chaco is a sparsely populated, hot and semiarid lowland tropical dry broadleaf forest natural region of the Río de la Plata basin, divided among eastern Bolivia, western Paraguay, northern Argentina, and a portion of the Brazilian states of Mato Grosso and Mato Grosso do Sul, where it is connected with the Pantanal region.

The name Chaco comes from the Quechua word chaqu meaning "hunting land", an indigenous language from the Andes and highlands of South America, and comes probably from the rich variety of animal life present throughout the entire region.

The wood of the palo santo from the Central Chaco is the source of oil of guaiac (a fragrance for soap).

In the central and northern Paraguay Chaco, occasional dust storms have caused major topsoil loss.

Eventually, Argentine Foreign Minister Carlos Saavedra Lamas mediated a ceasefire and subsequent treaty signed in 1938, which gave Paraguay three-quarters of the Chaco Boreal and gave Bolivia a corridor to the Paraguay River with the ability to use the Puerto Casado and the right to construct their own port.

[3] Mennonites immigrated into the Paraguayan part of the region from Canada in the 1920s; more came from the USSR in the 1930s and immediately following World War II.

The region is home to over 9 million people, divided about evenly among Argentina, Bolivia, and Brazil, and including around 100,000 in Paraguay.

This declines to seasonally flooded forests, at lower elevations, that are dominated by Schinopsis spp., a common plains tree genus often harvested for its tannin content and dense wood.

Other seasonally flooded ecosystems of this area include palm-dominated (Copernicia alba) savannas with a bunch grass-dominated herbaceous layer.

To the west, in the Semiarid/Arid Chaco, medium-sized forests consists of white quebracho (Aspidosperma quebracho-blanco) and red quebracho (Schinopsis lorentzii) with a slightly shorter subcanopy made up of several species from the family Fabaceae, as well as several arboreal cacti species that distinguish this area of the Chaco.

The Highlands of the Argentinian Chaco are made up of, on the dry, sunny side (up to 1800m), Schinopsis haenkeana woodlands.

Animals typically associated with tropical and subtropical forests are often found throughout the eastern Humid Chaco, including jaguars, howler monkeys, peccaries, deer, and tapirs.

Rotting logs, debris piles, old housing settlement, wells, and seasonal farm ponds are examples of such refugia.

[12] Two factors may substantially change the Chaco in the near future: low land valuations[13][14] and the region's suitability to grow fuel crops.

The feasibility of switchgrass is currently being studied by Argentina's Instituto Nacional de Tecnología Agropecuaria,[17] as is the Karanda'y palm tree in the Paraguayan Chaco.

[18] While advancements in agriculture can bring some improvements in infrastructure and employment for the region, loss of habitat and virgin forest is substantial and will likely increase poverty.

Since 2007, a law is supposed to regulate and control the cutting of timber in the Gran Chaco, but illegal logging continues.

[21] Among the aggressive investors in the Paraguayan Gran Chaco are U.S.-based agribusinesses Cargill Inc., Bunge Ltd., and Archer Daniels Midland Co.[22] A 2017 assessment found that 176,715 km2, or 22%, of the ecoregion is in protected areas.

The following Argentine provinces, Bolivian and Paraguayan departments, and Brazilian states lie in the Gran Chaco area, either entirely or in part.