The 11th Armored Cavalry Regiment ("Blackhorse Regiment") is a unit of the United States Army garrisoned at the Fort Irwin National Training Center in California. The regiment has served in the Philippine–American War, the Pancho Villa Expedition, World War II, the Vietnam War, Gulf War and Iraq War. The 11th ACR serves as the opposing force (OPFOR) for the Army and Marine task forces, and foreign military forces that train at Fort Irwin.

The OPFOR trained U.S. Army forces in mechanized desert warfare following a Soviet-era style threat until June 2002, when the OPFOR and the 11th Armored Cavalry Regiment changed to portraying an urban/asymmetrical warfare style of combat U.S. soldiers are facing in operations abroad. From June to December 2003, members of the 11th ACR deployed to Afghanistan, where they helped to develop and train the armor and mechanized infantry battalions of the Afghan National Army. These specialized units would defend the Afghan capital during the country's constitutional convention. In January 2005, the 11th ACR deployed to Iraq. The 11th ACR was not reorganized under the U.S. Army Combat Arms Regimental System, though it has been reorganized under the U.S. Army Regimental System.