Archaeological findings have attested human presence in the area from the Bronze Age; the first historical inhabitants were the Lusitanians, followed by the Celts, who came from east to the Pyrenees.
The migration of the Celtici is considered part of a third or fourth wave of Celts in the 4th century BCE: this migration occurred across modern-day Aragon and into modern-day Extremadura and Alentejo, displacing the proto-Celt Lusitanians who dominated the lands north of the Tagus, and skirting the Vettones lands that stretched from Zamora to Castelo Branco.