Ctenopterus is a genus of prehistoric eurypterid of the family Stylonuridae.

It contains only one species, Ctenopterus cestrotus from the Early Silurian of Otisville, New York, United States.

[1] Stylonurids, which lived from the Ordovician to Lower Permian periods, were small to very large forms with scales developing into tubercules and knobs.

The prosoma (head) exhibited variable shape, with arcuate compound eyes located subcentrally, or anteriorly.

All of its legs are walking legs; the second and third pairs are strongly developed, with a double row of numerous flat spines; the last pair is long, without spines.