The Kawasaki Ki-100 (キ100) is a single-seat single-engine monoplane fighter aircraft used by the Imperial Japanese Army Air Service (IJAAS) during World War II.

[4] A newly built variant, the Ki-100-Ib, was produced with a cut down rear fuselage during the last months of the war which equipped five home defence sentai.

At this point of the war, the IJAAS was in desperate need of effective interceptors to stop bombing raids over the Japanese mainland, so in October 1944 a decision was made to use the 1,120 kW (1,500 hp) Mitsubishi Ha-112-II (Kinsei ["Venus"] 60 series), a 14-cylinder, two-row radial engine.

Their solution was to use a second skin to form a fairing riveted to the fuselage to smooth out the airflow behind the cooling flaps and multiple exhaust stubs of the new engine cowling.

Without the need for the heavy coolant radiator and other fittings required for a liquid-cooled engine, the Ki-100 was 329 kg (725 lb) lighter than the Ki-61-II, reducing the wing loading from 189 kg/m2 (38.8 lb/ft2) to 175 kg/m2 (35.8 lb/ft2).

This had a positive effect on the flight characteristics, enhancing landing and takeoff qualities as well as improving manoeuvrability and reducing the turning radius.

[6] During March and April 1945, experienced instructors from the Akeno Army Flying School flew the Ki-100 in extensive tests against the Ki-84, which was the best IJAAS fighter then in operational service.

[4] The flight characteristics of the plane surpassed the Hien's in all but maximum speed, which was reduced by 29 km/h (18 mph) by the larger cross sectional area of the radial engine, and the model was ordered into production as the Goshikisen (Go=five; shiki=type; sentoki=fighter) or Army Fighter Type 5.

[7] Although its maximum speed in level flight was a bit slow for 1945, the Ki-100 could dive with North American P-51 Mustangs and maintain speed after pullout, unlike most Japanese fighters.Two remaining problems continued to hamper Japanese fighters towards the end of the war, these being unreliable electrical systems and poor radio equipment, and while the latter was never resolved, the Ki-100's electrical system was less of a problem than with other types.

A well-handled Ki-100 was able to outmanoeuvre any American fighter, including the P-51D Mustangs and Republic P-47N Thunderbolts, which escorted the B-29s over Japan, and was comparable in speed, especially at medium altitudes.

[13] During interception of high-flying B-29 Superfortresses (before the B-29s switched to low-level missions), the new fighters struggled, as the engine's performance still dropped off at high altitudes.

The most effective strategy against the B-29 Superfortress remained the exceedingly dangerous head-on attack, which left the fighter relatively stationary in the sights of the bomber's defensive guns, making it an easy target.

[15] On 25 July 1945, 18 244th Sentai Ki-100 fighters clashed with 10 VF-31 Grumman F6F Hellcats from the light aircraft carrier USS Belleau Wood in an air battle where the Ki-100 pilots claimed twelve victories with two losses.