The 1972–73 NHL season was the 56th season of the National Hockey League. Sixteen teams each played 78 games. For the first time since the collapse of the Western Hockey League in 1926, the National Hockey League had serious competition. A new professional hockey league, the World Hockey Association, made its season debut with 12 new teams, many of which were based in the same cities as NHL teams. Unlike the Western Hockey League, though, the new World Hockey Association would not challenge for the Stanley Cup. In response to the new league, the NHL hastily added two new teams in an unplanned expansion, the New York Islanders and Atlanta Flames, in an attempt to exclude the WHA from newly constructed arenas in those markets.