The Slender clingfish(Gastrocyathus gracilis) is a clingfish of the family Gobiesocidae, the only species in the genus Gastrocyathus.

This species grows to a length of 4.5 centimetres (1.8 in) TL.

Endemic to New Zealand, this species is apparently only found in beds of strap-fronded algae.

Harpacticoid copepods comprise the main component of their diet.

This Gobiesocidae-related article is a stub.