Phallostethus dunckeri is a species of fish in the family Phallostethidae.

Phallostethus dunckeri is recorded to be found in a freshwater environment within a pelagic depth range.

[2] The eggs of Phallostethus dunckeri are fertilised internally and then after laying they are attached to the substrate by adhesive filaments.

[4] It was described by Charles Tate Regan in 1913 with a type locality of the Muar River, Johor in Malaysia.

[5] Regan honoured the German ichthyologist Georg Duncker (1870–1953) of the Zoologisches Museum Hamburg, Duncker initially wrote about this species in 1904 but he was too busy to write a description so he passed some of his specimens on to Regan for him to describe.