National Hockey League rivalries are a cornerstone of the sport, primarily driven by geographic proximity, frequent matchups, on-ice incidents, and cultural or national pride. In the NHL's early days, intense Canadian rivalries emerged, notably between Montreal's French Canadiens and English Wanderers, before the league gained sole Stanley Cup ownership by 1926 and expanded into the U.S. The "Original Six" era (1942-1967) further solidified these animosities, as limited teams and low player turnover fostered deep-seated personal and team rivalries among the Boston Bruins, Chicago Blackhawks, Montreal Canadiens, Detroit Red Wings, New York Rangers, and Toronto Maple Leafs. Today, prominent examples include the historic "Battle of Ontario" between the Ottawa Senators and Toronto Maple Leafs, which dates back to 1890, and the "Battle of the QEW" between the Buffalo Sabres and Toronto Maple Leafs, fueled by their close 100-mile proximity.