Wikipedia
Bellovesus was a legendary Gallic king. He lived around 600 BCE and is remembered for invading northern Italy with his people during the legendary reign of the 5th king of Rome, Tarquinius Priscus (from 616 BCE to 579 BCE), although archeology would associate Gallic expansion into Italy to around 500 BCE.
The historical writer Livius marks that he was the son of the sister of the king Ambigatus. His family belonged to the tribe of Bituriges, which were at this time the most powerful Gaulic tribe and in each case placed therefore the king of all Gaul. In this time, the Gaulish people were suffering from overpopulation, so that it became necessary to open new settlement areas. Bellovesus and his brother Segovesus were entrusted with this task. While Segovesus was chosen by the gods — that is, by lot, got an indication to look in the Hercynian Forest for new areas to settle — Bellovesus was led to upper Italy.
Bellovesus allegedly led a group of six surplus tribes forward over the Alps: Bituriges, Arverni, Senones, Aedui, Ambarri, Carnutes, and Aulerci. The Alps represented an insurmountable hurdle for the course however first. Only after Bellovesus received support from the Greeks, who in the area of the Salyes had landed and established the port-city of Massilia ( Marseille) in c. 600 BCE, did Bellovesus follow a divine sign and succeed in the crossing of the Alps through a pass in the area of Taurini. Having arrived in Italy, the Gauls defeated the Etruscans at the Ticino River and settled in an area which was later called Insubria. Here Bellovesus founded the city of Mediolanum, the modern Milan.