The 15th Cavalry Regiment is a cavalry regiment of the United States Army. It was one of the Expansion Units originally established for the Spanish–American War, but has been a general workhorse unit ever since.

The 15th Cavalry Regiment was constituted on 2 February 1901 in the Regular Army, and organized on 12 February at the Presidio of San Francisco, California. Immediately after its organization, the 15th Cavalry embarked for the Philippines to quell an insurrection in the United States' newly acquired territory. The regiment's next action was part of the Cuban Pacification from 1906 to 1909, followed by duty along the Mexican border and the hunt for revolutionary leader Pancho Villa from December 1917 to March 1918.