In politics and military planning, a war effort is a coordinated mobilization of society's resources—both industrial and human—towards the support of a military force. Depending on the militarization of the culture, the relative size of the armed forces and the society supporting them, the style of government, and the famous support for the military objectives, such war effort can range from a small industry to complete command of society.

Although many societies were retroactively perceived to be engaged in a war effort, the concept was not generally used until the last decade of the 18th century, when the leaders of the French Revolution called for the levée en masse and a general mobilization of society to prevent monarchist forces from reclaiming control of the French government.

The concept was subsequently adapted and used by Russia, the United Kingdom, and the United States, especially during World War I and World War II. The term war effort was coined in conjunction with these efforts.