Sioux Indian chief of the Oglala tribe who was an able tactician and determined warrior in the Sioux resistance to the white man's invasion of the northern Great Plains.

As early as 1865 Crazy Horse was a leader in his people's defiance of U.S. plans to construct a road to the goldfields in Montana. He participated in the massacre of Captain William J. Fetterman and his troop of 80 men (Dec. 21, 1866) as well as in the Wagon Box fight (Aug. 2, 1867), both near Fort Phil Kearny, in Wyoming Territory. Refusing to honour the reservation provisions of the Second Treaty of Fort Laramie (1868), Crazy Horse led his followers to unceded buffalo country, where they continued to hunt, fish, and wage war against enemy tribes as well as whites.

When gold was discovered in the Black Hills, Dakota Territory, in 1874, prospectors disregarded Sioux treaty rights and swarmed onto the Indian reservation there. General George Crook (Crook, George) thereupon set out to force Crazy Horse from his winter encampments on the Tongue and Powder rivers in Montana Territory, but the chief simply retreated deeper into the hills. Joining Cheyenne forces, he took part in a surprise attack on Crook in the Rosebud valley (June 17, 1876), in southern Montana, forcing Crook's withdrawal.

Crazy Horse then moved north to unite with the main Sioux encampment of Chief Sitting Bull on the banks of the Little Bighorn River, where he helped annihilate a battalion of U.S. soldiers under Lieutenant Colonel George A. Custer (Custer, George Armstrong) (June 25, 1876). Crazy Horse and his followers then returned to the hill country to resume their old ways. He was pursued by Colonel Nelson A. Miles in a stepped-up army campaign to force all Indians to come to the government agencies. His tribe weakened by cold and hunger, Crazy Horse finally surrendered to General Crook at the Red Cloud Agency in Nebraska on May 6, 1877. Confined to Fort Robinson, he was killed in a scuffle with soldiers who were trying to imprison him in a guardhouse.