Kahoolawe (Hawaiian: kəˈhoʔoˈlɐve), anglicized as Kahoolawe (kɑːˌhoʊoʊˈlɑːweɪ,_-veɪ), is the smallest of the eight main volcanic islands of the Hawaiian Islands. Unpopulated, it lies about southwest of Maui. The island is long by wide, with a total land area of . Its highest point is the crater of Lua Makika, at the summit of Puu Moaulanui, about above sea level.
Kahoolawe is relatively dry, with an average annual rainfall of less than resulting from a combination of being too low to generate much orographic precipitation from the northeastern trade winds and lying in the rain shadow of eastern Maui's volcano, Haleakalā. More than one quarter of Kahoolawe has been eroded down to saprolitic hardpan soil, largely on exposed surfaces near the summit.
Historically, Kahoolawe was always sparsely populated, due to its lack of fresh water. During World War II and the following decades, it was used as a training ground and bombing range by the Armed Forces of the United States. After decades of protests, the U.S. Navy ended live-fire training exercises on Kahoʻolawe in 1990, and the whole island was transferred to the jurisdiction of the state of Hawaii in 1994. The Hawaii State Legislature established the Kahoʻolawe Island Reserve to restore and to oversee the island and its surrounding waters. Today Kahoʻolawe can be used only for native Hawaiian cultural, spiritual, and subsistence purposes. It has no permanent residents.
Kahoʻolawe is an extinct shield volcano, which formed during the Pleistocene epoch. It was once connected to the island of Maui Nui before splitting off about 300,000 years ago. Most of the island is covered by basaltic lava flows. A caldera is located in the eastern part of the island. The last confirmed volcanic activity on the island occurred about one million years ago, though eruptions could have occurred about 10,000 years ago.
Kahoʻolawe experiences a semi-arid climate (Köppen BSh).
Sometime around the year 1000, Kahoʻolawe was settled by Polynesians, and small, temporary fishing communities were established along the coast.