The Boulton Paul Defiant is a British interceptor aircraft that served with the Royal Air Force (RAF) during World War II. The Defiant was designed and built by Boulton Paul Aircraft as a "turret fighter", without any fixed forward-firing guns, also found in the Blackburn Roc of the Royal Navy.
In combat, the Defiant was found to be effective at destroying bombers, the role it was designed for, but was vulnerable to the Luftwaffe's more manoeuvrable, single-seat Messerschmitt Bf 109 fighters. The Defiant had been designed to destroy unescorted bombers by means of beam or ventral attacks and therefore lacked forward-firing armament, that proved to be a great weakness in daylight combat with fighters. It did, however, find success when it was converted to a night fighter. It eventually equipped thirteen squadrons in this role, compared to just two squadrons as a day-fighter, though this was mainly due to slow initial production. In mid-1942 it was replaced by better performing night-fighters, the Bristol Beaufighter and de Havilland Mosquito.
The Defiant continued to find use in gunnery training, target towing, electronic countermeasures and air-sea rescue. Among RAF pilots it had the nickname "Daffy".