Trigonoceras is an extinct genus of prehistoric nautiloids from the nautilid family Trigonoceratidae that lived during the Early Carboniferous in what is now western Europe.

Trigonoceras has a very loosely coiled gyroconic or cyrtoconic shell with a subtriangular cross section, as indicated by fragmentary specimens.

The venter on the outer rim or convex side is broad and transversely concave with angular shoulders; the sides which converge on a narrow dorsum are broadly convex.

The siphuncle is slightly dorsal of the center and is orthochoanitic.(Kummel,B.1964.)

A member of the Trigonoceratidae, Trigonoceras is also a component of the superfamily Trigonocerataceae