Ectillaenus is a genus of trilobites in the order Corynexochida.
These nektobenthic carnivores lived in the Ordovician period, from 478.6 to 449.5 Ma.
Species include:
Fossils of this genus have been found in the Ordovician sediments of Czech Republic, France, Morocco, Portugal, Spain and United Kingdom, as well as in the Arenig of the United Kingdom.