Cadwallon is a Welsh name derived from the Common Brittonic *Katuwellaunos (Proto-Celtic *Katu-weln?-mnos) "The One Who (-mnos) Leads (weln?-) in Battle (katu-)". The same name belonged to the Catuvellauni who lived in what is now Hertfordshire, one of the most powerful British polities in the Late Iron Age who led the resistance against the Romans in 43 CE and possibly against Caesar in 55 and 54 BCE as well.
Cadwallon is not to be confused with Caswallon, which derives from *Kai-weln?-mnos (the same name as Cassivellaunus), meaning "The Passionate Leader". Note that in Cornish, both Katuwellaunos(/Catuvellaunus) and Kaiwellaunos(/Cassivellaunus) give the form Kaswallon, which adds to the confusion.
Cadwallon may refer to: