Chaco (Spanish pronunciation: [ˈtʃako]; Wichi: To-kós-wet[3]), officially the Province of Chaco (Spanish: provincia del Chaco, Spanish pronunciation: [pɾo'βinsja dεl ˈtʃako]) is one of the 23 provinces in Argentina. Its capital and largest city, is Resistencia.[4] It is located in the north-east of the country.

It is bordered by Salta and Santiago del Estero to the west, Formosa to the north, Corrientes to the east, and Santa Fe to the south.[4] It also has an international border with the Paraguayan Department of Ñeembucú. With an area of 99,633 km2 (38,469 sq mi), and a population of 1,055,259 as of 2010, it is the twelfth most extensive, and the ninth most populated, of the twenty-three Argentine provinces.

In 2010, Chaco became the second province in Argentina to adopt more than one official language. These languages are the Kom, Moqoit and Wichí languages, spoken by the Toba, Mocovi and Wichí peoples respectively. Chaco has historically been among Argentina's poorest regions, and currently ranks last both by per capita GDP and on the Human Development Index.