The Wounded Knee Massacre, also known as the Battle of Wounded Knee, was a massacre of nearly three hundred Lakota people by soldiers of the United States Army. The massacre, part of what the U.S. military called the Pine Ridge Campaign, occurred on December 29, 1890, near Wounded Knee Creek (Lakota: Čhaŋkpé Ópi Wakpála) on the Lakota Pine Ridge Indian Reservation in South Dakota, following a botched attempt to disarm the Lakota camp. The previous day, a detachment of the U.S. 7th Cavalry Regiment commanded by Major Samuel M. Whitside approached Spotted Elk's band of Miniconjou Lakota and 38 Hunkpapa Lakota near Porcupine Butte and escorted them five miles (eight kilometers) westward to Wounded Knee Creek, where they made camp. The remainder of the 7th Cavalry Regiment, led by Colonel James W. Forsyth, arrived and surrounded the encampment. The regiment was supported by a battery of four Hotchkiss mountain guns. The Army was catering to the anxiety of settlers who called the conflict the Messiah War and were worried the Ghost Dance signified a potentially dangerous Sioux resurgence. Historian Jeffrey Ostler wrote in 2004, "Wounded Knee was not made up of a series of discrete unconnected events. Instead, from the disarming to the burial of the dead, it consisted of a series of acts held together by an underlying logic of racist domination."

On the morning of December 29, the U.S. Cavalry troops went into the camp to disarm the Lakota. One version of events claims that during the process of disarming the Lakota, a deaf tribesman named Black Coyote was reluctant to give up his rifle, claiming he had paid a lot for it. Black Coyote's rifle went off at that point; the U.S. Army began shooting at the Lakota. The Lakota warriors fought back, but many had already been stripped of their guns and disarmed.

By the time the massacre was over, more than 250 men, women and children of the Lakota had been killed and 51 were wounded (4 men and 47 women and children, some of whom died later); some estimates placed the number of dead as high as 300. Twenty-five soldiers also died and thirty-nine were wounded (six of the wounded later died). Twenty soldiers were awarded the Medal of Honor. In 2001, the National Congress of American Indians passed two resolutions condemning the military awards and called on the federal government to rescind them. The Wounded Knee National Historic Landmark, site of the massacre, has been designated a National Historic Landmark by the U.S. Department of the Interior. In 1990, both houses of the U.S. Congress passed a resolution on the historical centennial formally expressing "deep regret" for the massacre.