Iwo Jima (硫黄島, officially Iōtō ?, also frequently Iōjima listen (help·info): "sulfur island") is an island of the Japanese Volcano Islands chain, which makes up the southern end of the Ogasawara Islands. The island is located 1,200 kilometers (650 nautical miles) south of mainland Tokyo and administered as part of Ogasawara, one of eight villages of Tokyo. It is famous as the site of the February–March 1945 Battle of Iwo Jima between the United States and Japan during World War II, when the iconic photograph Raising the Flag on Iwo Jima was taken. The U.S. occupied Iwo Jima until 1968, when it was returned to Japan.

Iwo Jima was traditionally called Iwōtō (Iōtō). Prior to Japan's 1946 orthography reform, a historical spelling resulted in (approximately) Iwōtō (modern Iōtō). An alternative, Iwōjima (modern Iōjima)—where jima is an alternative pronunciation of tō (島, island?)—also appeared in nautical atlases. Japanese naval officers who arrived to fortify the island before the American invasion mistakenly called it Iwo Jima. In this way, the "Iwo Jima" pronunciation became mainstream and was the one used by American forces who arrived during World War II. Former island residents protested against this rendering, and the Ministry of Land, Infrastructure and Transport's Geographical Survey Institute debated the issue and formally announced on June 18, 2007, that the official Japanese pronunciation of the island's name would be reverted to the pre-war Iōtō. Moves to revert the pronunciation were sparked by the high profile films Flags of Our Fathers and Letters from Iwo Jima. The change does not affect how the name is written in Japanese (硫黄島?), only how it is pronounced.

The island has an approximate area of 21 km² (8 mi²) at 24°47′N 141°19′E / 24.783°N 141.317°E / 24.783; 141.317Coordinates: 24°47′N 141°19′E / 24.783°N 141.317°E / 24.783; 141.317. The most prominent feature is Mount Suribachi (摺鉢山, Suribachiyama?) on the southern tip, a vent that is thought to be dormant and is 166 m (546 ft) high. Iwo Jima is unusually flat and featureless for a volcanic island. Suribachi is the only obvious volcanic feature, as it is only the resurgent dome (raised center) of a larger submerged volcanic caldera. Eighty km north of the island is North Iwo Jima (北硫黄島, Kitaiōtō?, literally: "North Sulphur Island") and 60 km south South Iwo Jima (南硫黄島, Minamiiōtō?, "South Sulphur Island") making up the Volcano Islands group of the Ogasawara Islands. Just south of Minamiiōjima are the Mariana Islands.