Rengo is a city and commune located in the Zona Central of Chile, situated in the Cachapoal Province of the O'Higgins Region at a distance of 28 km (17 mi) south of the city of Rancagua and 114 km (71 mi) south of the national capital Santiago. It was named after the courageous Toqui Rengo for his particular bravery at the Battle of Lagunillas.
According to the 2002 census of the National Statistics Institute, Rengo spans an area of 591.5 km2 (228 sq mi) and has 50,830 inhabitants (25,311 men and 25,519 women). Of these, 37,075 (72.9%) lived in urban areas and 13,755 (27.1%) in rural areas. The population grew by 16.5% (7,213 persons) between the 1992 and 2002 censuses.