Map of the Roman province Maxima Sequanorum
(c. 300 AD), which comprised the territories of the Helvetii, Sequani
and several smaller tribes. The relative locations of the Helvetian pagi
Tigurini and Verbigeni, though indicated on the map, remain unknown.
A map of Gaul
in the 1st century BC, showing the relative positions of the Celtic tribes.
The Helvetii (Latin: Helvētiī [hɛɫˈweː.tjiː], anglicized Helvetians) were a Gallic tribe or tribal confederation occupying most of the Swiss plateau at the time of their contact with the Roman Republic in the 1st century BC. According to Julius Caesar, the Helvetians were divided into four subgroups or pagi. Of these Caesar only names the Verbigeni and the Tigurini, while Posidonius mentions the Tigurini and the Tougeni (Τωυγενοί). They feature prominently in the , with their failed migration attempt to southwestern Gaul (58 BC) serving as a catalyst for Caesar's conquest of Gaul.
The Helvetians were subjugated after 52 BC, and under Augustus, Celtic oppida, such as Vindonissa or Basilea, were re-purposed as garrisons. In AD 68, a Helvetian uprising was crushed by Aulus Caecina Alienus. The Swiss plateau was at first incorporated into the Roman province of Gallia Belgica (22 BC), later into Germania Superior (AD 83). The Helvetians, like the rest of Gaul, were largely Romanized by the 2nd century. In the later 3rd century, Roman control over the region waned, and the Swiss plateau was exposed to the invading Alemanni. The Alemanni and Burgundians established permanent settlements in the Swiss plateau in the 5th and 6th centuries, resulting in the early medieval territories of Alemannia (Swabia) and Upper Burgundy.