Ambicatus (or Ambigatos in Gaulish) is mentioned in the founding legend of Mediolanum (Milan) by Livy, whose source is Timagenes, as a king of the Bituriges, "kings of the world" as their name suggests, who ruled over the Celts in central Gaul, between Hispania and Germany, in the days of Tarquinius Priscus (the sixth century BCE). Ambicatus sent his sister's sons, Bellovesus and Segovesus, with many followers drawn from numerous tribes, to found new colonies in the Hercynian forest and in northern Italy, in the early sixth century BC. Bellovesus founded Mediolanum. If Ambicatus was an authentic historical figure, rather than a construct to express the linked origins of Celtic tribes in northern Italy and beyond the Alps, most likely he was the leader of the most powerful tribe in a military alliance, from which the Celtic colonizers of Italy were apparently drawn.
- Livius, Ab Urbe condita 5.34-35.3.
- The Bituriges had their capital in Avaricum, today Bourges.
- From bitu = world (cf. Welsh byd or Breton bed of same meaning) and rix = king (cognate to Latin rex)
- "The names Ambigatus, the very wise, Segovesus, having knowledge of victory, and Bellovesus are poetical names," Richard Wellington Husband observed, in "Kelts and Ligurians" Classical Philology 6.4 (October 1911), pp. 385-401.
- Bituriges, and the surrounding Arverni, Senones, Aedui, Ambarri, Carnutes and Aulerci, are noted by Livy.
- "The diffusion of the Ambicatus legend would help to preserve unity by recalling the mythic greatness of the past," J.A. McCulloch remarked, in The Religion of the Ancient Celts (1911), ch.II, pp 19ff.
- Smith, William (1867). "Ambigatus". In William Smith. Dictionary of Greek and Roman Biography and Mythology. 1. Boston: Little, Brown and Company. p. 138.
- Smith, William (1870). Dictionary of Greek and Roman Biography and Mythology. Boston: Little, Brown, and Company. p. 138.