The Wagon Box Fight was an engagement which occurred on August 2, 1867, in the vicinity of Fort Phil Kearny during Red Cloud's War. A party of twenty-six U.S. Army soldiers and six civilians were attacked by several hundred Lakota Sioux warriors. Although outnumbered, the soldiers were armed with newly supplied breech-loading Springfield Model 1866 rifles and lever-action Henry rifles, and had a defensive wall of wagon boxes to protect them. They held off the attackers for hours with few casualties, although they lost a large number of horses and mules driven off by the raiders.

Fort Phil Kearny was an outpost of the United States Army that existed in the late 1860s in present-day northeastern Wyoming along the Bozeman Trail. Construction began in 1866 on Friday, July 13, by Companies A, C, E, and H of the 2nd Battalion, 18th Infantry, under the direction of the regimental commander and Mountain District commander Colonel Henry B. Carrington.