The Nakajima J1N1 Gekkō (月光, "Moonlight") is a twin-engine aircraft used by the Imperial Japanese Navy during World War II.

In mid-1938 the Japanese Imperial Navy requested a twin-engine fighter designed to escort the principal bomber used at the time, Mitsubishi G3M "Nell".

Moreover, at the time, the potential of the "Zero", then still under development, remained to be evaluated, stressing the need for a long-range escort fighter, much as the Luftwaffe had done with the Messerschmitt Bf 110 Zerstörer, introduced the year before.

The prototype left the factory in March 1941 equipped with two 843 kW (1,130 hp) Nakajima Sakae 21/22, 14-cylinder radial engines.

Four of these machine guns were mounted in two rear-mounted powered turrets, the weight of which reduced the performance of the aircraft considerably.

In early 1943, Commander Yasuna Kozono (小園 安名) of the 251st Kōkūtai in Rabaul came up with the idea of installing 20 mm cannons, firing upwards at a 30-degree angle in the fuselage.

This arrangement was effective against B-17 Flying Fortress bombers and B-24 Liberators, which usually had Sperry ball turrets for ventral defense.

The Gekkō's existence was not quickly understood by the Allies, who assumed the Japanese did not have the technology for night fighter designs.

The J1N1-S was used against B-29 Superfortresses in Japan, though the lack of good radar and insufficient high-altitude performance handicapped it since, usually, only one pass could be made against the higher-speed B-29s.

Records show that after arriving aboard the USS Barnes, air intelligence officials assigned Gekkō 7334 to Langley Field, Virginia, on 8 December 1945.

At least one other test flight took place before the Army Air Forces flew the fighter to an empty former Douglas C-54 factory at Park Ridge, Illinois, for storage.