Nancagua (Spanish pronunciation: [naŋˈkaɣwa]) is a Chilean city and commune in Colchagua Province, O'Higgins Region.
According to the 2002 census of the National Statistics Institute, Nancagua spans an area of 111.3 km (43 sq mi) and has 15,634 inhabitants (7,959 men and 7,675 women). Of these, 9,264 (59.3%) lived in urban areas and 6,370 (40.7%) in rural areas. The population grew by 8.5% (1,220 persons) between the 1992 and 2002 censuses.
As a commune, Nancagua is a third-level administrative division of Chile administered by a municipal council, headed by an alcalde who is directly elected every four years. The 2021-2024 alcalde is Mario Bustamante.