Brennus or Brennos is the name of two Gaulish chieftains, famous in ancient history:
- Brennus, chieftain of the Senones, a Gallic tribe originating from the modern areas of France known as Seine-et-Marne, Loiret, and Yonne; in 387 BC, in the Battle of the Allia, he led an army of Cisalpine Gauls in their attack on Rome.
- Another Brennus was one of the leaders of the army of Gauls who attempted to invade and settle in the Greek mainland in 278 BC. After a looting spree and after managing to pass Thermopylae by encircling the Greek army and forcing it to retreat he made his way to the rich treasury at Delphi but he was defeated by the re-assembled Greek army. Brennus was heavily injured at the battle of Delphi and committed suicide there.
The linguistic origins of the name are unclear, despite two theories linking it to Welsh words. Despite suggestions by scholars as early as the 12th century AD, including one by Geoffrey of Monmouth in his Historia Regum Britanniae, Brennus is not likely to share a common origin with the Welsh personal name Bran (or Brân) meaning "crow"; the similarity of the names is deemed to be superficial. Recurrence of the name Brennus makes it possible that it was a title rather than a proper name. However, despite assertions by some 19th-century scholars, Brennus and the modern Welsh word for "king", brenin (earlier breenhin) are not related.[1] Brenin is instead derived from the Celtic *brigantinos, meaning "(someone) pre-eminent, outstanding".[2]