Gomphoceras is a questionable nautiloid cephalopod genus assigned to the Oncocerida.

Gomphoceras, named by Sowerby in 1839, is generally short but rapidly expanding, straight to slightly endogastric, with a gibbous body chamber such that all sides are convex.

The aperture as vertically transverse, with a hyponomic sinus on a low spout-like process and a larger rounded dorsal sinus connetected above.

Tetrameroceras and Trimeroceras, both oncocerids, are similar in general form, but have more complex apertures.

This prehistoric cephalopod-related article is a stub.