The Curtiss P-40 was an American single-engine, single-seat, all-metal fighter and ground attack aircraft that first flew in 1938. It was used by the air forces of 28 nations, including those of most Allied powers during World War II, and remained in front line service until the end of the war. By November 1944, when production of the P-40 ceased, 13,738 had been built, all at Curtiss-Wright Corporation's main production facility at Buffalo, New York.

The P-40 design was a modification of the previous Curtiss P-36; this reduced development time and enabled a rapid entry into production and operational service.

Warhawk was the name the United States Army Air Corps adopted for all models, making it the official name in the United States for all P-40s. The British Commonwealth and Soviet air forces used the name Tomahawk for models equivalent to the P-40B and P-40C, and the name Kittyhawk for models equivalent to the P-40D and all later variants.

The P-40's lack of a two-stage supercharger made it inferior to Luftwaffe fighters such as the Messerschmitt Bf 109 or the Focke-Wulf Fw 190 in high-altitude combat and it was rarely used in operations in Northwest Europe. Between 1941 and 1944, however, the P-40 played a critical role with Allied air forces in three major theaters: North Africa, the Southwest Pacific and China. It also had a significant role in the Middle East, Southeast Asia, Eastern Europe, Alaska and Italy. The P-40's high-altitude performance was not as critical in those theaters, where it served as an air supremacy fighter, bomber escort and fighter bomber.

P-40s first saw combat with the British Commonwealth squadrons of the Desert Air Force (DAF) in the Middle East and North African campaigns, during June 1941. The Royal Air Force's No. 112 Squadron was among the first to operate Tomahawks, in North Africa, and the unit was the first to feature the "shark mouth" logo, copying similar markings on some Luftwaffe Messerschmitt Bf 110 twin-engine fighters. Inspired by the RAF's 112 Squadron's initial Allied usage of them in North Africa, and by the Luftwaffe's even earlier use of it, both via Allied wartime newspaper and magazine article images, the "shark-mouth" logo's usage on the sides of the P-40's nose was most famously used on those used by the Flying Tigers in China.

In theatres where high-altitude performance was less important, the P-40 proved an effective fighter. Although it gained a post-war reputation as a mediocre design, suitable only for close air support, more recent research including scrutiny of the records of individual Allied squadrons indicates that the P-40 performed surprisingly well as an air superiority fighter, at times suffering severe losses, but also taking a very heavy toll on enemy aircraft. The P-40 offered the additional advantage of low cost, which kept it in production as a ground attack fighter long after it was obsolete in air superiority.

As of 2008, 19 P-40s remain airworthy.