The fairy martin (Petrochelidon ariel) is a member of the swallow family of passerine birds which breeds in Australia.

The adult has an iridescent blue back, brown wings and tail, a rufous crown and nape, and a whitish rump.

The sexes are similar, but young birds are duller and browner, with a paler forehead and pale fringes to the back and wing feathers.

Nests are constructed in natural holes in dead trees, riverbanks, cliff faces or rock crevices, but increasingly in artificial sites on bridges, in culverts and pipes, and on buildings.

The nest is a retort- or bottle-shaped structure, made from up to a thousand mud pellets and lined with dried grasses and feathers.