Palaeomylus (meaning 'ancient grinder') is an extinct Devonian ptychodontid placoderm fish.

There are seven species accepted in this genus:[1][2] The generic name is derived from Greek (Palaeo, meaning "ancient") and (mylos, meaning "grinder").

Not to be confused with the junior homonym Palaeomylus (Meng, Wyss, Hu, Wang, Bowen & Koch, 2005), which is an early diverging member of the mammal group Glires.

[3] P. greenei, P. crassus, and the type species P. frangens were originally classified as a species of Rhynchodus, before being moved to a new genus, Palaeomylus, in 1891.

P. predator was found near Gerolstein, Germany.