St. Paul's fingerfin (Nemadactylus monodactylus), is a species of marine ray-finned fish, traditionally regarded as belonging to the family Cheilodactylidae, the members of which are commonly known as morwongs.

The St. Paul’s fingerfin was first formally described as Chaetodon monodactylus in 1819 by the Scottish Army surgeon and botanist Dugald Carmichael with the type locality given as Tristan da Cunha.

[3] Genetic and morphological analyses strongly support the placement of Nemadactylus in the family Latridae, alongside almost all of the other species formerly classified in the Cheilodactylidae.

[4] St Paul’s fingerfin has an oblong and compressed body, its shape altering as the fish grows.

[1] The St Paul’s fingerfin occurs around the Tristan Islands and the Vema Seamount in the South Atlantic Ocean and off Amsterdam and St Paul Island in the southwestern Indian Ocean and on the Austral Seamount and Walters Shoal.