The crag martins are five species of small passerine birds in the genus Ptyonoprogne of the swallow family.

1/ Dusky crag martin (Nhạn nâu hung, Ptyonoprogne concolor)

Hirundinidae: Latin hirundo swallow.
The genus name Ptyonoprogne is derived from the Greek ptuon (πτύον), "a fan", referring to the shape of the opened tail, and Procne (Πρόκνη), a mythological girl who was turned into a swallow.