The Romans started pushing into what is now Swiss territory at the beginning of the 3rd century BC when southern Ticino came under their rule after the defeat of Hannibal. About 75 years later the Romans took the Rhone valley, including Geneva, in order to protect the route from Italy to Spain.

In 58 BC Julius Caesar prevented the Helvetians from migrating out of the Swiss Plateau. His successes in the area were continued after his death by the Emperor Augustus. The Rhaetians came under Roman rule in 15BC.

The Romans then attempted to move further north still, into what is now Germany, but were forced back. The Rhine became the border of the Roman empire and remained so until the first years of the fifth century.

The Romans referred to the Celts in general as Gauls.