The Stanley Cup (French: La Coupe Stanley) is the championship trophy awarded annually to the National Hockey League (NHL) playoff winner. Originally commissioned in 1892 as the Dominion Hockey Challenge Cup, the trophy is named for Lord Stanley of Preston, then–Governor General of Canada, who awarded it 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. The first Cup was awarded in 1893 to Montreal HC, and subsequent winners from 1893 to 1914 were determined by challenge games and league play. Professional teams then became eligible to challenge for the Stanley Cup in 1906. In 1915, the two professional ice hockey organizations, the National Hockey Association (NHA) and the Pacific Coast Hockey Association (PCHA), reached a gentlemen's agreement in which their respective champions would face each other annually for the Stanley Cup. After a series of league mergers and folds, it was established as the de facto championship trophy of the NHL in 1926 and then the de jure NHL championship prize in 1947.

There are actually three Stanley Cups: the original bowl of the "Dominion Hockey Challenge Cup", the authenticated "Presentation Cup", and the "Replica Cup" at the Hall of Fame. The NHL has maintained effective control over both the trophy itself and its associated trademarks. Nevertheless, the NHL does not actually own the trophy, but instead uses it by agreement with the two Trustees of the Cup. The NHL has registered trademarks associated with the name and likeness of the Stanley Cup, although the league's right to outright own trademarks associated with a trophy it does not own has been disputed by some legal experts. The original bowl was made of silver and is 18.5 centimetres (7.28 inches) in height and 29 centimetres (11.42 inches) in diameter. The current Stanley Cup, topped with a copy of the original bowl, is made of a silver and nickel alloy; it has a height of 89.54 centimetres (35.25 inches) and weighs 15.5 kilograms (34.5 lb / 2 st 6½ lb).

Unlike the trophies awarded by the other major professional sports leagues of North America, a new Stanley Cup is not made each year; winners keep it until a new champion is crowned. It is unusual among trophies, in that it has the names of all of the winning players, coaches, management, and club staff engraved on its chalice. Initially, a new band added each year caused the trophy to grow in size, earning the nickname "Stovepipe Cup". In 1958 the modern one-piece Cup was designed with a five-band barrel which could contain 13 winning teams per band. To prevent the Stanley Cup from growing, when the bottom band is full, the oldest band is removed and preserved in the Hockey Hall of Fame, and a new blank band added to the bottom. It has been referred to as The Cup, Lord Stanley's Cup, The Holy Grail, or facetiously (chiefly by sportswriters) as Lord Stanley's Mug. The Stanley Cup is surrounded by numerous legends and traditions, the oldest of which is the celebratory drinking of champagne out of the cup by the winning team. Some traditions by fans include the Calgary "C of Red", and the "Winnipeg White Out".

Since the 1914–15 season, the Cup has been won a combined 95 times by 18 active NHL teams and five defunct teams. Prior to that, the challenge cup was held by nine different teams. The Montreal Canadiens have won the Cup a record 24 times and are the most recent Canadian-based team to win the cup, having won it in 1993. The Stanley Cup was not awarded in 1919 because of a Spanish flu epidemic, and in 2005, as a consequence of the 2004–05 NHL lockout.