Ceraurus is a genus of cheirurid trilobite of the middle and, much more rarely, the upper Ordovician. They are commonly found in strata of the lower Great Lakes region. These trilobites have eleven thoracic segments, a very small pygidium and long genal and pygidial spines. The taxonomy of the genus is problematic, as the many variations of eye placement, decoration patterns of pustules, and spine length call the genus' defining characteristics into question. Ceraurus may, in fact, be at least four genera: Ceraurus sensu stricto, and the genera, Gabriceraurus, Bufoceraurus and Leviceraurus.