The Wire-tailed Swallow (Hirundo smithii) is a small passerine bird in the swallow family. Swallows are somewhat similar in habits and appearance to other aerial insectivores, such as the related martins and the unrelated swifts (order Apodiformes).

Wire-tailed Swallow breeds in Africa south of the Sahara and in tropical southern Asia from the Indian subcontinent east to southeast Asia. It is mainly resident, but populations in Pakistan and northern India migrate further south in winter.

This species is an uncommon vagrant to Sri Lanka.

This bird is found in open country near water and human habitation. Wire-tailed Swallows are fast flyers and they generally feed on insects, especially flies, while airborne. They are typically seen low over water, with which they are more closely associated than most swallows.

The neat half-bowl nests are lined with mud collected in the swallows' beaks. They are placed on vertical surfaces near water under cliff ledges or more commonly on man-made structures such as buildings and bridges.

The clutch is three to four eggs in Africa, up to five in Asia (Turner and Rose). These birds are solitary and territorial nesters, unlike many swallows, which tend to be colonial.

This striking species is a small swallow at 14cm in length. It has bright blue upperparts, except for a chestnut crown and white spots on the tail. The underparts are white, with darker flight feathers. There is a blue mask through the eye.

This species gets its name from the very long filamentous outermost tail feathers, which trail behind like two wires. Sexes manifest similar appearances, but the female has shorter "wires". Juveniles have a brown crown, back and tail. The Asian form, H. s. filifera, is larger and longer-tailed than the abundant African H. s. smithii.

The scientific name of this bird is after Professor Chetien Smith, a Norwegian botanist, who was a member of the British expedition to the Congo River in 1816, led by James Kingston Tuckey.