Arctic charr (Salvelinus alpinus) is a cold-water salmonid that was recorded in the Red Data Book of threatened species in France although its geographical distribution continues to extend and it has been established now in 138 lakes in France. Lake Allos (a French lake in Department of Alpes-de-Haute-Provence, 2229 m a.s.l.) possessed Arctic charr of unknown origin. Therefore the origin was researched in the present paper. Till the 1910s this fish had not been known from Lake Allos. There was a project of Arctic charr introduction in 1922 (but result is unknown). For the first time this fish was reported in Lake Allos in 1923. In 1924 the lake was further restocked with the same species. Arctic charr therefore seems not to be native to this lake. In 1800 only three French lakes were reported to contain Arctic charr (Lakes Leman, Bourget and Paladru). Salvelinus alpinus was in fact a fish of low altitude in France. The notion of "Arctic charr, a high-altitude fish" was not due to a natural distribution but to a long history of artificial stockings into high-altitude lakes through the 20th century in France and Switzerland or since the Middle Age in Austrian Tyrol and Italy. Since its introduction during the 1920s Arctic charr lives in Lake Allos. Its original strain would be from Leman, and genetic pool seems not to have been disturbed since that time because no further stockings would have been carried out. Lake Allos therefore contains a pure strain of Arctic charr (of Lake Leman). After several decades of acclimatization, S. alpinus formed two distinct populations in Lake Allos. Population biology and genetics are important for providing data necessary for protection and management of Arctic charr and Lake Allos. Together these belong to natural heritage of France.