The World at War is a 1942 documentary film produced by the Office of War Information's Bureau of Motion Pictures. One of the earliest long length films made by the United States government during the war, it attempted to explain the large picture of why the United States was at war, and the various causes and circumstances which brought the war into being.

The documentary opens with visuals of the attack on Pearl Harbor and its immediate aftermath. It then traces the previous decade of American involvement in the war, including Kuhn's address at the German-American Bund, speeches by isolationist U.S. Senators Nye and Wheeler, Japan's invasion of China, Italy's war on Ethiopia, Hitler's Anschluss, the Spanish Civil War, the Munich Agreement, the rape of Czechoslovakia, and the invasion of Poland. In covering the outbreak of total war, the film uses footage from Nazi propaganda films Feldzug in Polen and Sieg im Westen.

It was a precursor to the better known six-part Why We Fight propaganda film series directed by Frank Capra.