The 61st Fighter Squadron was constituted as the 61st Pursuit Squadron as part of the 56th Pursuit Group at Savannah, Georgia, on 15 January 1941. The squadron immediately began training for its wartime missions under III Fighter Command, rapidly transitioning through the Seversky P-35, Curtiss P-36 Hawk, Bell P-39 Airacobra and Curtiss P-40 Warhawk aircraft. On 7 December 1941, the 61st stepped up to defend the Southeastern United States from anticipated enemy air attack while it converted to the Republic P-47 Thunderbolt aircraft and prepared to deploy overseas. In November 1942, P-47 Thunderbolt dive test pilots achieved 725 mph, faster than the speed of sound.
It was redesignated 61st Fighter Squadron on 15 May 1942, and deployed to RAF Kings Cliffe (AAF-367), England on 9 January 1943. It was declared operationally ready two months later and flew its first combat missions 13 April. The squadron was given fuselage code “HV” and operated from several RAF stations during the war, flying the P-47C Thunderbolt as an VIII Fighter Command bomber-escort unit initially for B-17 Flying Fortresses and beginning in 1944 for B-24 Liberators attacking enemy targets in Occupied Europe. From 1943 to 1945, the 61st produced 19 aces, the highest of any squadron in Europe, destroying 248 aircraft in the air and 67.5 aircraft on the ground. In 1944, it was recognized as the first fighter squadron in the European theater to score over 100 victories. After the end of the war in Europe, the squadron demobilized in England, and was inactivated as an administrative unit on 18 October 1945.