Marine Helicopter Squadron One (HMX-1) is a United States Marine Corps helicopter squadron responsible for the transportation of the president and vice president of the United States, heads of state, Department of Defense officials, and other VIPs as directed by the Marine Corps and White House Military Office. A Marine helicopter with the president aboard uses the call sign "Marine One". Previously, HMX-1 was also tasked with operational test and evaluation (OT&E). This task was reassigned to VMX-1 in Yuma, Arizona; since the contract award of the new presidential helicopter in 2014 to Sikorsky Aircraft, however, HMX-1 has assumed the temporary role of OT&E for this platform, because of its unique nature and mission. The VH-92A first flew in 2017 and is expected to be operational sometime after 2022. Nicknamed "Nighthawks", HMX-1 is headquartered at Marine Corps Air Facility Quantico, Virginia, and maintains detachments at Joint Base Anacostia–Bolling in Washington, D.C., and Joint Base Andrews Naval Air Facility in Maryland.

The United States Marine Corps (USMC), also referred to as the United States Marines, is the maritime land force service branch of the United States Armed Forces responsible for conducting expeditionary and amphibious operations through combined arms, implementing its own infantry, artillery, aerial, and special operations forces. The U.S. Marine Corps is one of the eight uniformed services of the United States.