Sergeant William Foster (1832 – July 16, 1880) was a British-born soldier in the U.S. Army who served with the 4th U.S. Cavalry during the Texas–Indian Wars.
Following a one-day march to the North Fork of the Red River, a lodge encampment of around 280 Mow-wi Comanche warriors was discovered.
As a result of MacKenzie's victory, the Mow-wi formally surrendered at Fort Sill ending 17 years of warfare.
Foster was among those who distinguished themselves in the fight and, with eight other members of his regiment, received the Medal of Honor for "gallantry in action".
Foster eventually left the military and settled in San Francisco, California, where he died on July 16, 1880, at the age of 48.