The protomonaxonid sponge Pirania is an iconic member of the Burgess Shale community, but recent discoveries show that piraniids are morphologically diverse and also occur in Ordovician strata. Here we establish three new piraniid genera on the basis of Ordovician material from China, Wales, Scotland and Morocco: Auraeopirania gen. nov., Cannapirania gen. nov. and Pellipirania gen. nov. We also establish eight new species: Pirania? peregrinata sp. nov. (Lower Ordovician Ningkuo Formation, China); P.? ericia sp. nov. (Lower Ordovician Afon Gam Biota, Wales); Auraeopirania pinwyddeni gen. et sp. nov. (Middle Ordovician Llanfallteg Biota, Wales); A. pykitia gen. et sp. nov. (Upper Ordovician, Scotland); A. sciurucauda gen. et sp. nov. (Early Ordovician, China); Cannapirania canna gen. et sp. nov. (Middle Ordovician Llanfawr Mudstones, Wales); C. vermiformis gen. et sp. nov. (Upper Ordovician Anji Biota, China); and Pellipirania gloria gen. et sp. nov. (Lower Ordovician Fezouata Biota, Morocco). Piraniids have now been widely reported (South China, Avalonia, Laurentia and Gondwana) from Ordovician strata, but in Cambrian strata have been documented only from the Burgess Shale. The Burgess Shale species Pirania muricata appears to be among the most derived members of the Piraniidae, implying a substantial hidden Cambrian diversity of piraniids. Over the family's history there is a tendency for species to become smaller and inhabit deeper-water environments.