Orthocerida, from Ancient Greek ὀρθός (orthós), meaning "straight", and κέρας (kéras), meaning "horn", also known as the Michelinocerida, is an order of extinct orthoceratoid cephalopods that lived from the Early Ordovician (490 million years ago) possibly to the Late Triassic (240 million years ago). The Eocene fossil Antarcticeras is sometimes considered a descendant of the orthocerids although this is disputed. They were most common however from the Ordovician to the Devonian.

A fossil found in the Caucasus was previously assigned to Orthocerida, extending the range to the Early Cretaceous, but has since been reassigned to the order Mixosiphonata.

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