Dumnovellaunus or Dubnovellaunus was a king ruling in south eastern England during the British Iron Age.

Evidence from coin distribution indicates he ruled over Kent east of the River Medway although a different issue of coinage bearing his name has also been found in Essex. Other coins found in Kent suggest other rulers there, one perhaps called Vodenos. Dumnovellaunus ruled following the death of Tasciovanus in the last few years BC. Theories involve him seizing a portion of Tasciovanus' Catuvellauniian territory or him being granted the kingdom of east Kent by Cunobelinus, Tasciovanus' successor.

According to the Monumentum Ancyranaum he and Tincommius, a king of the Atrebates tribe fled to Rome as supplicants to Augustus around AD 7. The reason is unclear although the political instability in the region at the time suggests he was deposed. Tincommius had been driven out of his capital at Silchester by Eppillus who in turn was also forced from power and moved to Kent to supplant Dumnovellanus.

Cunobelinus appears to have then united Kent and Essex in his kingdom, granting Dumnovellaunus' realm to his own son, Adminius.