The name of the the trophy awarded to the National Hockey League team that first qualifies for the playoffs at the end of the regular season, and then wins all of the playoff series, is called the 'Stanley Cup'. Since teams compete from both the US and Canada, in French, the trophy is called 'La Coupe Stanley'.

It is the oldest existing trophy to be awarded to a professional sports franchise. Originally commissioned in 1892 as the 'Dominion Hockey Challenge Cup', the trophy is named after Lord Stanley of Preston, then-governor General of Canada. He donated it as an award to Canada's top-ranking amateur ice hockey club, which the entire Stanley family supported, with the sons and daughters playing and promoting the game.

Professional teams then became eligible to play for the 'Stanley Cup' in 1906. Further changes occurred in 1915, when the two professional ice hockey organizations, the National Hockey Association (NA) and the Pacific Coast Hockey Association (PCHA), reached an agreement- annually, their respective champions would face each other, and the winner received the 'Stanley Cup'.

After a series of league mergers and folds, it was established as the 'de facto' (in fact) championship trophy of the National Hockey League (NHL) in 1926. Then the 'Stanley Cup' became the 'de jure' (by right) NHL championship trophy prize in 1947.

More Info: en.wikipedia.org