Welsh Indians are a supposed tribe of Native Americans of Welsh origin. Several Native American groups have been identified as having Welsh origins, most prominently the Mandans of North Dakota. Welsh Indians are usually claimed to have descended from a colony founded by prince Madoc in 1170. Apart from tall tales, no evidence has ever been found for their existence.
According to legend, Madoc was the son of Owain Gwynedd, a great but belligerent Welsh king. After his death Madoc's brothers fell out with each other and continuously warred for their father's succession. Wary of all the bloodshed, Madoc decided to leave Wales and sailed west, where he reached an unknown land. He left 120 men as a colony and returned to Wales. There he gathered ten ships full of men, women and livestock and returned to his colony. Since then Madoc was never heard of again.
Apparently Madoc was a somewhat well-known figure in Medieval poetry, but the only references to him surviving today date from after Christopher Columbus. The oldest surviving record of Madoc's adventures date from a history of Wales published by Humphrey Llwyd in 1559, supposedly based on ancient Welsh sources. In the 16th and 17th century Madoc's story was occasionally used by the British crown as a legitimation of its colonization of North America. Though the pope had awarded most of the Americas to Spain, the British claimed the Spanish' claim was illegitimate because Madoc rather than Columbus was the real discoverer of the Americas. Locations identified as the site of Madoc's colony include most of the North American East Coast, as well as the Gulf coast of Alabama, Mexico's Yucatán peninsula and the Bahamas.
From the 17th century onwards an encounter with Welsh Indians became a common theme in stories about the Anglo-American conquest of North America. Most such stories have a similar plot: a Welshman sets out to the hinterland where he gets taken prisoner by Native Americas. As they are about to execute him, he says something (usually a prayer) in Welsh, which the Natives recognize as their own language and release him. Needless to say, any follow-up expeditions have failed to encounter any Welsh Indians.
Other "evidence" involves archaeological finds from the 1700s, including memorials written in Welsh or Caucasian remains wearing European armor. However, any such pieces of evidence will have been stolen/lost sometime in the 20th century.
The first mention of Welsh Indians dates from 1568, by the early 20th century it had become clear that no such people existed. Embarrassingly, in 1953 the Daughters of the American Revolution erected a plaque in Mobile Bay, Alabama commemorating Madoc's discovery and colonization of that site in 1170. The plaque has since been removed.