The river martins are a distinct subfamily Pseudochelidoninae within the swallow and martin bird family Hirundinidae. They possess a number of distinct features which mark them out from other swallows and martins, namely their robust legs and feet, and stout bill.
There are two species:
- African River Martin Pseudochelidon eurystomina, found around the River Congo in Congo and Gabon
- White-eyed River Martin Pseudochelidon sirintarae, of Thailand in South-east Asia.
When the African River Martin was first discovered in the 19th Century, it was not thought to be a member of the swallow and martin family; Hartlaub placed it with the Rollers, and later authors either placed it in its own family, or with the Woodswallows. Study of the anatomy of the species by Lowe (1938) revealed that the species was closest to the swallows and martins, but sufficiently distinct to be placed in a separate subfamily.
The White-eyed River Martin was discovered as recently as 1968 and is only known from specimens and anecdotal evidence - no modern ornithologists have seen the species in the wild, and its breeding grounds are unknown; it may be extinct.
The two species are usually considered to belong to a single genus, Pseudochelidon due to their having a number of structural similarities; Brooke (1972) proposed that White-eyed River Martin be placed in a separate monotypic genus Eurochelidon, but this has not been adopted by other authors.