The Calaveras River is a river in the San Joaquin Valley of California. It flows roughly southwest for 51.9 miles (83.5 km) from the confluence of its north and south forks in Calaveras County to its confluence with the San Joaquin River in the city of Stockton. The Spanish word calaveras means "skulls." The river was said to have been named by Spanish explorer Gabriel Moraga in 1806 when he found many skulls of Native Americans along its banks. He believed they had either died of famine or been killed in tribal conflicts over hunting and fishing grounds.