The War Measures Act was a Canadian statute that allowed the government to assume sweeping emergency powers. When the act was invoked, citizens could be arrested and imprisoned without the benefit of trial or even a stated explanation. It essentially created a state of martial law throughout the country.

The act was invoked three times in Canadian history: World War I, World War II, and most controversially at the request of the government of the province of Quebec during the October Crisis of 1970.

The act was later repealed and replaced with the Emergencies Act in 1988.