Ctenorhachis (Greek for "comb spine") is an extinct genus of the family Sphenacodontidae.

[1] Ctenorhachis lived in the Early Permian epoch.

Two specimens are known that have been found from the Wichita Group outcropping in Baylor and Archer counties, north-central Texas.

Articulated vertebrae from the holotype specimen possess blade like neural spines that are greatly enlarged, although not nearly to the extent that can be seen in more derived sphenacodontids such as Dimetrodon and Secodontosaurus, in which they form a large sail.

As suggested in the original description of the genus, Ctenorhachis may represent a short-spined sexual dimorph, although the authors find this unlikely.