El Teniente

El Teniente
	Caletones copper smelter at El Teniente
	Location within Chile
Location	Sewell, Cachopoal, Chile; 34°05′16″S 70°23′15″W / 34.08778°S 70.38750°W;
Products	Copper
Type	Underground
Opened	1819
Company	Codelco

Pouring slag from Caletones onto the dump, El Teniente

"The ore is mined by a highly developed caving system and carried down to the main transportation level through an elaborate system of ore passes."

El Teniente (Spanish for "The Lieutenant") is the world's largest underground copper mine, located in the Andes Mountains of central Chile at an elevation of 2,300 metres (7,500 ft) above sea level. It is operated by the state-owned mining company Codelco and constitutes the largest division of its operations. Mining at the site dates back to at least 1819, but large-scale industrial extraction began in 1906 under U.S. ownership, initially through the Braden Copper Company and later Kennecott Copper Corporation. In 1971, during the presidency of Salvador Allende, Chile nationalized its copper industry and acquired full ownership of El Teniente. The mine contains more than 3,000 kilometres (1,900 mi) of tunnels and employs about five thousand workers. It was the site of the 1945 Smoke Tragedy, the deadliest metal mining accident in Chilean and world history. Since 2011, El Teniente has been undergoing a major expansion known as the New Mine Level project, which aims to extend operations deeper into the mountain without halting production. As of 2023 it is the third most productive copper mine in Chile after Los Pelambres and Escondida.