The Japanese sparrowhawk (Tachyspiza gularis) is a bird of prey in the family Accipitridae which also includes many other diurnal raptors such as eagles, buzzards and harriers. It was formerly placed in the genus Accipiter. The bird is known by many alternative names such as the Japanese lesser, Asiatic, or Eastern sparrowhawk. This species is a small raptor with broader and rounder wings and a shorter tail. Its total length measures 23–30 centimetres (9.1–11.8 in). It has a dark back and whitish underside with brown-grey barring and red-brown colouring on the sides in males, and with heavier brown barring on the abdomen in females. Both sexes have a stripe across the throat, but its more obvious in the female. Is it typically identified by its appearance, but occasionally produces a chattering kiki-kik-kik... sound. This species generally breeds in parts of Russia, Korea, Japan, and China. There are three subspecies of Japanese sparrowhawk that differ by distribution and appearance. The species is globally listed as least concern, although it is listed as endangered in Japan and protected in China.

The Japanese sparrowhawk was formally described in 1845 by the zoologists Coenraad Jacob Temminck and Hermann Schlegel in Philipp Franz von Siebold's Fauna Japonica. They specified the scientific name Astur (Nisus) gularis, where Nisus was an alternative possible genus: it had been introduced by Georges Cuvier in 1800. The specific epithet gularis is Modern Latin meaning "of the throat" or "throated".

The Japanese sparrowhawk was formerly placed in the genus Accipiter. In 2024 a comprehensive molecular phylogenetic study of the Accipitridae confirmed earlier work that had shown that the genus was polyphyletic. To resolve the non-monophyly, Accipiter was divided into six genera. The genus Tachyspiza was resurrected to accommodate the Japanese sparrowhawk together with 26 other species that had previously been placed in Accipiter. The resurrected genus had been introduced in 1844 by the German naturalist Johann Jakob Kaup. The genus name combines the Ancient Greek ταχυς (takhus) meaning "fast" with σπιζιας (spizias) meaning "hawk".

The species is closely related to the Besra (Tachyspiza virgata). For a time, it was thought the Japanese sparrowhawk was a migratory subspecies of the Besra, but that was disproved. It was then thought that the Besra and Japanese sparrowhawk were two very closely related species. However, it was recently discovered that they are not as closely related despite their similar appearances and might be more closely related to the collared sparrowhawk (Tachyspiza cirrocephala) of Australasia.  

Three subspecies are recognised:

Adult male Japanese sparrowhawks measure between 23–30 centimetres (9.1–11.8 in) in length with a wingspan measuring 46–58 centimetres (18–23 in), and weigh 92–142 grams (3.2–5.0 oz). They have a small, curved bill, long pointed wingtips, a relatively short-tail and long, slim legs and toes. Adult males have black-slate upperparts with white on the nape of the neck. They have whitish underparts with grey-brown and washed red-brown barring. Adult males have yellow legs and their tail feathers are grey with four dark bands. They have red-orange eyes with brown-grey patches on the cheeks, and a subtle line on their white throats.  

In flight, adult males appear to have a faint red-brown wash on either side of the chest, distinct brown-grey bars on wing-linings and flanks, and their flight feathers have thin bands.

Adult females are larger than their male counterparts, weighing around 111–193 centimetres (44–76 in). They have brown upperparts, but they do not have any red-brown barring on their underparts or sides. Adult females have a white body and wing-linings with brown-grey barring. They have yellow eyes, and like the adult males, have yellow legs and a stripe over the throat, but it is more obvious on adult females.