The histerical province o Colchagua wis one o the regions o Chile, bitween 1826 an 1976. Its capital wis located i San Fernando during most o its existence. For some years, Curicó an Rancagua were capitals o Colchagua. The province o Colchagua wis ane o the former, primitive eicht provinces o Chile (Coquimbo, Aconcagua, Santiago, Colchagua, Maule, Concepción, Valdivia, an Chiloé) creatit bi the federal laws o 31 January 1826.
Durin its early years, Colchagua wis dividit intae the departments o San Fernando (cap. San Fernando), Curicó (cap. Curicó), an Talca (cap. Talca). Althouch the title o provincial capital wis disputit bi San Fernando, Curicó an Talca, dependin on the desirit residence o the intendant, a September 1840 decree establishit San Fernando as the definitive capital. I July 1974, a new reform took place, directit bi the military dictatorship o Augusto Pinochet, wha creatit regions. On 1 January 1976, the new VI Región (Sixth Region) came intae existence, wi the territory o former provinces o O'Higgins an Colchagua.