The Iran-Iraq War, also known as the Iraqi Imposed War and Iranian Revolutionary War in Iran, was a war between the armed forces of Iraq and Iran lasting from September 1980 to August 1988. It was commonly referred to as the Persian Gulf War until the Iraq-Kuwait conflict of (1990A 91), and for a while thereafter as the First Persian Gulf War. The Iraq-Kuwait conflict, while originally known as the Second Persian Gulf War, later became known simply as the Persian Gulf War.

The war began when Iraq invaded Iran on 22 September 1980 following a long history of border disputes and fears of Shia insurgency influenced by Khomeini's Islamic republic. Although the Iraqis attacked without formal warning, they failed to make progress and were soon repelled by the Iranians. Despite several calls for a ceasefire by the United Nations Security Council, hostilities continued until 20 August 1988; the last prisoners of war were exchanged in 2003. The war altered regional and even global politics.

The war is also noted for being very similar to World War I. Tactics used included trench warfare, manned machine-gun posts, bayonet charges, use of barbed wire, human wave attacks and Iraq's extensive use of chemical weapons (such as mustard gas) against Iranian troops and civilians as well as Iraqi Kurds. It is believed that more than a million Iraqi and Iranian soldiers as well as civilians died in the war with many more injured and wounded.