Rancagua (Spanish pronunciation: [raŋˈka.ɡwa]) is a city and commune in central Chile and part of the Rancagua conurbation. It is the capital of the Cachapoal Province and of the O'Higgins Region, located 87 km (54 mi) south of the national capital of Santiago. In 2002, it's population was 214,344. The main economic activities range from mining, tourism, agriculture, wood industry, food production and services to minor industrial activities. The city also serves as the administrative and legal center of the region.

Rancagua was founded by José Antonio Manso de Velasco, who founded several cities in the central area of Chile. The city's original name was Villa Santa Cruz de Triana.

The city is famous in Chilean history as the scene of the Disaster of Rancagua of 1814, when Chilean forces fighting for independence from Spain were defeated, marking the beginning of the period known as the Reconquista (an attempt by Spain to regain control of Chile).

In the wake of the February 27, 2010 earthquake, Cuba set up a temporary hospital in the city with a medical brigade of 27 doctors and 9 staff.