Hardmanoceras is a tarphycerid genus belonging to the Trocholitidae from the upper Lower Ordovician to possibly the lower Middle Ordovician, found in Western Australia.

Hardmanoceras is like Discoceras but prominently ribbed and with a depressed whorl section.

The ultimate portion is slightly divergent, not an uncommon characteristic of tarphycerids.

Harmanoceras was named by Teichert and Glenister in 1952.

This prehistoric nautiloid-related article is a stub.