Onychoprion

Onychoprion is a genus of four species of terns in the family Laridae. The genus name is from Ancient Greek , "claw" or "nail", and , "saw". As a group, they have been variously called "brown-winged terns" or "brown-backed terns", though only one species is actually brown; the other three are dark grey or black.

==Species== Although the genus Onychoprion was first described in 1832 by Johann Georg Wagler, the species in the genus were generally retained within the larger genus Sterna, the genus that holds most terns, until a study in 2005 showed that this treatment was paraphyletic, with these four species less closely related to typical Sterna terns, than several other terns long treated in other genera like Chlidonias and Larosterna.