Why We Fight is a series of seven propaganda films produced by the US Department of War from 1942 to 1945, during World War II. It was originally written for American soldiers to help them understand why the United States was involved in the war, but US President Franklin Roosevelt ordered distribution for public viewing.

A propaganda film is a film that involves some form of propaganda. Propaganda films spread and promote certain ideas that are usually religious, political, or cultural in nature. A propaganda film is made with the intent that the viewer will adopt the position promoted by the propagator and eventually take action towards making those ideas widely accepted. Propaganda films are popular mediums of propaganda due to their ability to easily reach a large audience in a short amount of time. They are also able to come in a variety of film types such as documentary, non-fiction, and newsreel, making it even easier to provide subjective content that may be deliberately misleading.