Leif Erikson, also known as Leif the Lucky (c. 970s – c. 1018 to 1025), was a Norse explorer who is thought to have been the first European to set foot on continental America, approximately half a millennium before Christopher Columbus. According to the sagas of Icelanders, he established a Norse settlement at Vinland, which is usually interpreted as being coastal North America. There is ongoing speculation that the settlement made by Leif and his crew corresponds to the remains of a Norse settlement found in Newfoundland, Canada, called L'Anse aux Meadows, which was occupied approximately 1,000 years ago.

Leif's place of birth is unknown, although it is assumed to have been in Iceland. His father, Erik the Red, founded the first Norse settlement in Greenland, where Leif was later raised. Following his voyage to Vinland and the subsequent death of his father, Leif became chief of the Greenland settlement. He had two known sons: Thorgils, born in the Hebrides; and Thorkell, who succeeded him as Greenland's chieftain.

Leif was the son of Erik the Red and his wife Thjodhild (Old Norse: Þjóðhildur), and, through his paternal line, the grandson of Thorvald Ásvaldsson. When Erik the Red was young, his father was banished from Norway for manslaughter, and the family went into exile in Iceland (which, during the century preceding Leif's birth, had been colonized by Norsemen, mainly from Norway). Leif was also a distant relative of Naddodd,^{[unreliable source?]} who discovered Iceland.

Leif's year of birth is often estimated in the c. 970s. Though his birthplace is not accounted for in the sagas, it is likely he was born in Iceland, where his parents met—probably somewhere on the edge of Breiðafjörður, and possibly at Haukadalur Valley, where his mother's family was based. It was in this valley that Erik cleared land and built the farmstead Eiríksstaðir, in c. 970.

Erik was later banished from Iceland and sailed west to a place he named Greenland. He then briefly returned to Iceland to bring his family and other colonists back with him to Greenland, establishing its first permanent settlement in 986. Leif grew up on the family estate Brattahlíð in the Eastern Settlement of Greenland. He had two brothers, whose names were Thorstein and Thorvald, and a sister, Freydís. Tyrker, one of Erik's thralls, had been specially trusted to keep charge of Erik's children, as Leif later referred to him as his "foster father."

The Saga of Erik the Red and the Saga of the Greenlanders, both thought to have been written around 1200, contain detailed, but sometimes conflicting accounts of the voyages to Vinland (usually interpreted as coastal North America). These sagas are generally regarded as works of literature, rather than purely historical accounts, with scholars debating their factual accuracy. The only known strictly historical mentions of Vinland appear in Adam of Bremen's historical treatise (c. 1075) and in the Book of Icelanders (c. 1122) by Ari the Wise, though both are merely passing references.

According to this saga, Leif discovered Vinland after being blown off course on his way from Norway to Greenland. Before this voyage, Leif had spent time at the court of Norwegian King Olaf Tryggvesson, where he had converted to Christianity. When Leif encountered the storm that forced him off course, he had been on his way to introduce Christianity to the Greenlanders. After they had arrived at an unknown shore, the crew disembarked and explored the area. They found wild grapes, self-sown wheat, and maple trees. Afterwards, they loaded their ship with samples of these newly-found goods and sailed east to Greenland, rescuing a group of shipwrecked sailors along the way. For this act, and for converting Norse Greenland to Christianity, Leif earned the nickname "Leif the Lucky". Leif did not return to Vinland, but others from Greenland and Iceland did, including Thorfinn Karlsefni.

According to this saga, Leif was not the first European to discover Vinland. Instead Bjarni Herjólfsson and his crew—on a voyage from Iceland to Greenland—were overtaken by wind and fog, missed the southern tip of Greenland, and encountered an unknown coast. Believing it to be somewhere other than Greenland, they did not disembark but rather continued to sail and found two additional coasts that did not correspond with their understanding of Greenland. After sailing back east, they eventually made it to their original destination, and then told of their discoveries.