Brennus (or Brennos) is the name of two Gaulish chieftains famous in ancient history:
The linguistic origins of the name are unclear, despite two different theories linking it to Welsh words. Brennus is not likely to share a common origin with the Welsh personal name Bran (or Brân) meaning 'crow', despite suggestions by scholars as early as 12th Century, when Geoffrey of Monmouth (in his Historia Regum Britanniae) suggested that Brennus was connected to Bran. The similarity of the names is superficial. Recurrence of the name Brennus makes it possible that it was a title rather than a proper name. However, Brennus and the modern Welsh word for "king", brenin (earlier breenhin) are not related, despite assertions by some 19th-century scholars.Brenin is instead derived from the Celtic *brigantinos, meaning '(someone) pre-eminent, outstanding'.
Examples of the name Brennus and variants of it may include:
The name was given to the French battleship Brennus (commissioned in 1896).