The Boulton & Paul P.66 was a design for a general purpose aircraft, to replace the numerous Westland Wapati and Fairey Gordon biplanes.
The P.66 was designed in response to specification G.4/31 of June 1931 (modified in September 1931), which called for an aircraft capable of serving as an army co-operation aircraft, torpedo bomber, dive bomber, light day and night bomber, photographic aircraft, reconnaissance aircraft and casualty evacuation aircraft.
The P.66 was a streamlined shoulder-wing monoplane that would have been powered by either a Jupiter FFAM or XFBM or Panther radial engines, each using a Townend ring. The pilot's open cockpit was placed just in front of the wing. In order to incease the ease of maintenance the horn balanced rudder and elevators were interchangeable.
A wind tunnel model of the P.66 was built, but no prototype followed. The G.4/31 contest was won by the Vickers 253, but this was also rejected for production, and eventually the contract went to the Vickers Wellesley.