Marine Medium Tiltrotor Squadron 561 (VMM-561) was a medium-lift squadron of the United States Marine Corps flying the Bell-Boeing V-22 Osprey. Known as the "Pale Horse", it was part of Marine Aircraft Group 16 and based out of Marine Corps Air Station Miramar in California. They were scheduled to move to Okinawa in 2012. The squadron previously served as a training unit during the Vietnam War but was previously deactivated with the retirement of the HUSS from active service.