49th Parallel is a 1941 British and Canadian war drama film. It was the third film made by the British filmmaking team of Michael Powell and Emeric Pressburger. It was released in the United States as The Invaders. The British Ministry of Information approached Michael Powell to make a propaganda film for them, suggesting he make "a film about mine-sweeping". Instead, Powell decided to make a film to help sway opinion in the then-neutral United States. Said Powell, "I hoped it might scare the pants off the Americans" and thus bring them into the war. Screenwriter Emeric Pressburger remarked, "Goebbels considered himself an expert on propaganda, but I thought I'd show him a thing or two". Powell persuaded the British and Canadian governments and started location filming in 1940, but by the time the film appeared, in March 1942, the United States, which had been trying to stay out of the war in Europe, had been drawn into taking sides against Germany.

The original choice to play the German officer, Lieutenant Hirth, was their production company's stalwart Esmond Knight. Knight had become involved in training Local Defence Volunteers (better remembered as the Home Guard) after the evacuation of Dunkirk and, in late 1940, he was accepted for training with the Royal Navy. That training would have conflicted with work on 49th Parallel.

Anton Walbrook as "Peter" donated half his fee to the International Red Cross. Raymond Massey, Laurence Olivier and Leslie Howard all agreed to work at half their normal fee, because they felt it was an important propaganda film. TCM's Rob Nixon observes that "One of the reasons for the movie's high quality is the superb ensemble cast, most of them major British stars working for drastically reduced wages because they believed in the film".

This is the only time that Canadian-born Massey played a Canadian on screen.