The 1919 Stanley Cup was canceled after many Montreal players came down
with the Spanish flu.

The Stanley Cup has been canceled before in the hockey championship’s
history, which dates back to 1894. The 1919 Stanley Cup finals between the
Montreal Canadiens and Seattle Metropolitans had to be cancelled due to the
players on the Montreal Canadiens being ill with the Spanish flu, a
worldwide outbreak which affected approximately 45,000 people in Canada
alone. When it was cancelled, five games had already been played in the
series: two wins for each team, along with one tie. National Hockey League
(NHL) Hall of Famer Joe Hall of the Montreal Canadiens died of the Spanish
flu four days after the cancellation. The Stanley Cup was also cancelled in
2005, due to a lockout by team owners.