Cristobal Colon, aka Christopher Columbus: four voyages over some 12 years, a photo by trudeau on Flickr.
The voyages of Columbus initiated European colonization of the American continents, and are thus of great significance in world history, says Wikipedia.
Christopher Columbus was a navigator and an admiral for Castile, a country that later founded modern Spain.
He made four voyages to the Americas, with his first in 1492, which resulted in what is widely referred to as the Discovery of the Americas.
The discovery of the Americas has variously been attributed to others. For example, the Vikings (c. 1000) had previously established a settlement at L'Anse aux Meadows, Newfoundland.
While Columbus was not the first European to voyage to the New World and did not actually reach the mainland until his third voyage in 1498 (when he reached South America, and the fourth voyage, when he reached Central America), his discoveries led to the major European sea powers sending expeditions to the New World to build trade networks and colonies and to convert the native people to Christianity.
Columbus died an unfulfilled man. About 1500 the king and queen fired him as colonial governor because he insisted on enslaving and killing indigenous peoples.