The Grumman F4F Wildcat was an American carrier-based fighter aircraft that began service with both the United States Navy and the British Royal Navy (as the Martlet) in 1940. First used in combat by the British in Europe, the Wildcat was the only effective fighter available to the United States Navy and Marine Corps in the Pacific Theater during the early part of World War II in 1941 and 1942. (Although the Brewster Buffalo was the Navy's first monoplane fighter, it proved disappointing in combat. It was withdrawn very early in the war and replaced by Wildcats as they became available.) With a top speed of 318 mph (512 km/h), the Wildcat was outperformed by the faster and more nimble 331 mph (533 km/h) Mitsubishi A6M Zero, but its ruggedness, coupled with tactics such as the Thach Weave, resulted in an air combat kill-to-loss ratio of 5.9:1 in 1942 and 6.9:1 for the entire war.
Lessons learned from the Wildcat were applied to the faster F6F Hellcat which could outperform the Zero on its own terms. The Wildcat continued to be built throughout the remainder of the war to serve on escort carriers, where larger and heavier fighters could not be used.