El Callao (; Spanish pronunciation: [kaˈʎa.o] or [kaˈʝa.o]) is the chief seaport of Peru. The city is also called Provincia Constitucional (Constitutional Province), the only province of the Callao Region. The Historic Centre of Callao is located 15 km (9.3 mi) west of Historic Centre of Lima , the country's capital, and is part of the Lima Metropolitan Area. Callao borders Lima Province on the north, east and south, and the Pacific Ocean on the west.
El Callao was founded by Spanish colonists in 1537, just two years after Lima (1535). It soon became the main port for Spanish commerce in the Pacific. The origin of its name is unknown; both Indian (particularly Yunga, or Coastal Peruvian) and Spanish sources are credited, but it is certain that it was known by that name since 1550. Other sources point to the similarity with the Portuguese word calhau [pebble], having a similar sound.
At the height of the Viceroyalty, virtually all goods produced in Peru, Bolivia, and Argentina were carried over the Andes by mule to Callao, to be shipped to Panama, carried overland, and then transported on to Spain via Cuba.