Marine Fighter Attack Training Squadron 501 (VMFAT-501) is a training squadron in the United States Marine Corps, consisting of 27 F-35B Lightning II aircraft and serves as the Fleet Replacement Squadron. Known as the "Warlords," the squadron is based at Marine Corps Air Station Beaufort, South Carolina and falls administratively under Marine Aircraft Group 31 and the 2nd Marine Aircraft Wing. The squadron has assumed the lineage of VMFA-451 which was originally known as the "Blue Devils" and saw action during World War II and Operation Desert Storm. They were decommissioned on 31 January 1997.

A Fleet Replacement Squadron (FRS), is a unit of the United States Navy or Marine Corps that trains Naval Aviators, Naval Flight Officers (NFOs) and enlisted Naval Aircrewmen on the specific front-line aircraft they have been assigned to fly. Students, referred to as Replacement Pilots, Replacement Flight Officers or Replacement Aircrew are either newly winged aviators, aviators transitioning from one type aircraft to another, or aviators returning to the cockpit after a period of non-flying. After completing the training regimen, graduates are assigned to fleet squadrons. Additionally, FRSs are responsible for training aircraft mechanics, providing replacement aircraft for fleet squadron attrition, and standardizing maintenance and aircraft operations.