The Battle of Iwo Jima (19 February – 26 March 1945) was a major battle in which the United States Marine Corps and United States Navy landed on and eventually captured the island of Iwo Jima from the Imperial Japanese Army (IJA) during World War II. The American invasion, designated Operation Detachment, had the purpose of capturing the island with its two airfields: South Field and Central Field.

The Japanese Army positions on the island were heavily fortified, with a dense network of bunkers, hidden artillery positions, and 18 km (11 mi) of tunnels. The American ground forces were supported by extensive naval artillery and had complete air supremacy provided by U.S. Navy and Marine Corps aviators throughout the battle.

The five-week battle saw some of the fiercest and bloodiest fighting of the Pacific War.

The Japanese combat deaths numbered three times the number of American deaths, but uniquely among Pacific War Marine battles, the American total casualties (dead and wounded) exceeded those of the Japanese. Of the 21,000 Japanese soldiers on Iwo Jima at the beginning of the battle, only 216 were taken prisoner, some of whom were captured only because they had been knocked unconscious or otherwise disabled. Most of the remainder were killed in action, but it has been estimated that as many as 3,000 continued to resist within the various cave systems for many days afterwards until they eventually succumbed to their injuries or surrendered weeks later.Despite the bloody fighting and severe casualties on both sides, the American victory was assured from the start. Overwhelming American superiority in numbers and arms as well as complete air supremacy—coupled with the impossibility of Japanese retreat or reinforcement, as well as sparse food and supplies—permitted no plausible circumstance in which the Japanese could have ultimately won the battle.The action was controversial, with retired Chief of Naval Operations William V. Pratt stating that the island was useless to the Army as a staging base and useless to the Navy as a fleet base. The Japanese continued to have early-warning radar from Rota island, which was never invaded, and the captured air field was barely used. Experiences with previous Pacific island battles suggested that the island would be well defended, and thus casualties would be significant.

Joe Rosenthal's Associated Press photograph of the raising of the U.S. flag at the top of the 169 m (554 ft) Mount Suribachi by six U.S. Marines became an iconic image of the battle and the American war effort in the Pacific.