(thôr'fĭn kärl'sĕvnē), fl. 1002–15, Icelandic leader of an attempt to colonize North America. He appeared in Greenland in 1002 and married Gudrid, widow of one of the sons of Eric the Red. He set out c.1010 with an expedition consisting of three ships and 160 men to settle in Vinland, which Leif Ericsson had discovered a few years before.
Thorfinn's expedition is recorded in the "Saga of Eric the Red" in the collection of sagas known as Hauksbok, and in a narrative interpolated in the "Saga of Olaf Tryggvason" in the Flateyjarbok. According to the former, which has been favored by most scholars, the expedition came first to a region they called Helluland. Then they passed on to a wooded country which they named Markland, sailed by sandy, desolate beaches called Furdustrands, and settled for the winter in a bay called Straumfjord.
Still seeking the land of grapes, they proceeded southward the next spring until they reached a place called Hop. There they found vines, and there they settled for the next winter, selecting a spot up a river that widened into a lake. Several encounters with the natives, however, in which two of their number were killed, induced them to abandon Hop in the spring and return to Straumfjord, where they spent the third winter. One of the ships, commanded by Thorhall, had deserted the first year after a disagreement and had met disaster in Ireland. With the prospect of attack, plus growing dissension, it was decided to abandon the whole attempt. Returning by Markland, Thorfinn's ship reached Greenland safely; the other was wrecked in the Irish Sea and part of its crew saved.
Much effort has been spent in attempts to identify the lands visited by Thorfinn and to discover his wintering sites, but no theory has won general acceptance. Places from Labrador to New England have been suggested, but such identifications are little more than guesses. There is also divergence on the dates assigned to Thorfinn's expedition.
See bibliography under Leif Ericsson and Vinland.