The black-backed dwarf kingfisher (Ceyx erithaca), also known as the three-toed kingfisher, is a pocket-sized bird in the family Alcedinidae. It was formerly considered as conspecific with the rufous-backed dwarf kingfisher and together the species complex was known by the English name "oriental dwarf kingfisher".

This tropical kingfisher is a partial migrant that is endemic to parts of the Indian Subcontinent and Mainland Southeast Asia. It resides in lowland forests, typically near streams or ponds, where it feeds upon insects, spiders, worms, crabs, fish, frogs, and lizards. It is easily distinguishable from other birds in its range due to its red bill, yellow-orange underparts, lilac-rufous upperparts, and blue-black back.

The black-backed dwarf kingfisher is one of the smallest known kingfisher species. It is only slightly larger than a medium-sized hummingbird and measures 12.5–14 cm (4.9–5.5 in) in length (including bill and tail). Females typically weigh 14-16g and males 14-21.5g, making the males slightly larger. The two sexes are otherwise alike and sexual dimorphism is not present. Both males and females have a black spot on the forehead; blue and white patches on the side of the neck; a lilac-rufous crown, rump, and tail; a dark blue back and wings; a white chin and throat; pale yellow-orange underparts; a dark brown iris; and red legs, feet, and bill. Juveniles are duller and have less lilac colouring; a white chin, throat and belly; yellow-orange bill with pale tip; and blue scapulars and wing-coverts. This species of kingfisher has three toes, explaining why it is sometimes called the three-toed kingfisher, however, there are other kingfishers which also have three toes. The toe-count in these kingfisher species does not appear to be adaptive. The vocalization is a high pitched, shrill "tsriet-tsriet" or soft "tjie-tjie-tjie" in flight.