Richmondichthys is an extinct genus of large prehistoric marine ray-finned fish known from the Early Cretaceous.

It contains a single species, R. sweeti from the late Albian-aged Allaru and Toolebuc Formations of Queensland, Australia.

[1][2] At over 2 metres (6.6 ft) in length,[3] it is the largest known member of the Aspidorhynchidae, a group of primarily marine ray-finned fishes that were dominant throughout the latter half of the Mesozoic.

Unlike other aspidorhynchid genera which are known to have had wide distributions, Richmondichthys appears to have been restricted to the Eromanga Sea.

Following a decade of study, the fossil was returned to the Kronosaurus Korner museum in Richmond to be put on display.