This legendary leader of the Celts' expedition against Rome in 386 BC. J.-C. According to an anecdote reported by Livy and other authors, Brennos, convinced that the weights used by the Romans to weigh the ransom of a thousand pounds of gold obtained for the departure of the Gallic army were rigged, would have added his heavy sword by declaring "vae victis" ("woe to the vanquished").
Commander-in-chief, with Akichorios, of the central body of the Celts' expedition against Macedonia and Greece, in 280 BC. He invaded Dardania and Peonia and moved in 279 BC. AD to Greece, where left, following a disagreement, twenty thousand men under the leadership of Leonnorios and Lutarios. Headed towards Delphi, the sanctuary of Apollo supposed to conceal immense treasures, the part of the Celtic army commanded by Brennos (sixty-five thousand men according to Trogue Pompey) crossed, despite the resistance offered by the Athenians and the Phocidians, the defiles of Thermopylae and oeta, but failed in front of the sanctuary. The real reasons for the failure were perhaps winter and illness. Wounded himself, Brennos managed to fall back and join Akichorios' troops somewhere in southern Macedonia. He will commit suicide around the beginning of 278 BC. AD in Heraclea, south of Mount Orbelos, while the Celtic army will continue its retreat towards Thrace. He would have been the leader of the Tolistobogiens people, one of the Galatian peoples settled in Asia Minor following these events. However, Strabo reports the opinion of older authors that Brennos was a Prausian.