The Battle of the Little Bighorn, fought on June 25 and 26, 1876, along the Little Bighorn River in southeastern Montana Territory, was the defining clash of the Great Sioux War of 1876. A combined Lakota Sioux, Northern Cheyenne, and Arapaho force defeated the U.S. Army’s 7th Cavalry after Lieutenant Colonel George Armstrong Custer attacked before converging Army columns could unite. In a contested landscape tied to Native homelands, Crow alliances, and U.S. expansion, the battle became a devastating Army defeat: Custer and many of his men were killed. Its broken terrain shaped confused fighting, and its legacy endures as a symbol of Native resistance and the violence of westward expansion.