Phylloceras is an extinct genus of ammonoid cephalopods belonging to the family Phylloceratidae.

They were almost smooth and the ornamentation was virtually absent or, at most, represented by simple growth lines barely visible.

The striking sinuous suture lines were characteristic of this genus.

They are reminiscent, in some ways, of the leaves of plants (hence the name Phylloceras, which means " leaf-horn").

Fossils of species within this genus have been found all over the world, particularly in Western Europe.