Ukrainian Canadian internment
In World War I, 8,579 male "aliens of enemy nationality" were interned, including 5,954 Austro-Hungarians, most of whom were probably ethnic Ukrainians. Many of these internees were used for forced labour in internment camps. See Ukrainian Canadian internment.

During World War II, Canada followed the U.S. lead in interning residents of Japanese and Italian ancestry. The Canadian government also interned citizens it deemed dangerous to national security. This included both fascists (including Canadians such as Adrien Arcand who had negotiated with Hitler to obtain positions in the government of Canada once Canada was conquered), Montreal mayor Camilien Houde (for denouncing conscription) and union organizers and other people deemed to be dangerous Communists. Such internment was made legal by the Defence of Canada Regulations, Section 21 of which read:

The Minister of Justice, if satisfied that, with a view to preventing any particular person from acting in a manner prejudicial to the public safety or the safety of the State, it is necessary to do so, may, notwithstanding anything in these regulations, make an order [...] directing that he be detained by virtue of an order made under this paragraph, be deemed to be in legal custody.
There were internment camps near Petawawa, Ontario; Kananaskis, Alberta;and Hull, Quebec.