Enniskillenus is an extinct genus of prehistoric billfish from the Eocene of Europe.

It contains a single species, E. radiatus from the Early Eocene-aged London Clay of England.

[1][2] The species was first improperly named without a description (as Ptychocephalus radiatus) by Agassiz (1833), and later assigned as an indeterminate member of Palaeorhynchus by Woodward (1901).

[3] It was properly described by Casier in 1966,[3] who placed it in the new genus Enniskillenus, named in honor of William Cole, 3rd Earl of Enniskillen, who collected fossil fish and donated specimens to the British Museum.

[4] Although often often placed in the primitive billfish family Palaeorhynchidae, most specimens of Enniskillenus do not preserve enough traits for a refined classification, though their vertebral morphology and rostra confirm that they are at least billfish.