The Bell D-188A (unofficial military designations XF-109/XF3L) was a proposed eight-engine Mach 2–capable vertical take-off and landing (VTOL) tiltjet fighter that never proceeded past the mock-up stage.

In 1955, Bell Aircraft was requested by both the USAF and the US Navy to develop a VTOL/STOVL supersonic, all-weather fighter-bomber and defence interceptor.

[citation needed] The aircraft was unconventional, and consisted of a long, thin, area ruled fuselage with a large fin and all-moving stabilators in the tail.

Bleed air from the fuselage engine compressors would have been directed to a pair of thrusters in the nose and two more in the tail to aid in pitch, roll and yaw movements.

Armament would have consisted of two 20mm cannon in the fuselage, an internal weapons bay and eight wing hard points for missiles and other ordnance.