Grammatonotus is a genus of marine ray-finned fishes belonging to the family Callanthiidae, which includes the splendid perches and groppos.

Grammatonotus was first proposed as a monospecific genus in 1905 by the American ichthyologist Charles Henry Gilbert when he described the new species Grammatonotus laysanus,[1] its type locality given as near Laysan Island in the Leeward Hawaiian Islands,[2] which he also designated as the type species of the new genus.

[3] The 5th edition of Fishes of the World classifies Grammatonotus as one of two genera in the family Callanthiidae, which it places in the order Spariformes.

[3] Grammatonotus groppos are ovoid to elongated in shape, with short, rounded snouts.

[3] These are rather small fishes with the largest species being G. laysanus which has a maximum published standard length of 12.8 cm (5.0 in).