In 406 the Iberian Peninsula was invaded by Germanic peoples consisting of Vandals, Swabians, and Alans, a non-Germanic people of Iranian stock who had attached themselves to the Vandals. Within two years, the invaders had spread to the west coast. The Swabians were primarily herders and were drawn to Galicia because the climate was similar to what they had left behind. The Vandals settled to the north of Galicia but soon left with the remnants of the Alans for the east. After the departure of the Vandals, the Swabians moved southward and settled among the Luso-Romans, who put up no resistance and assimilated them easily. The urban life of the citânias gave way to the Swabian custom of dispersed houses and smallholdings, a pattern that is reflected today in the land tenure pattern of northern Portugal. Roman administration disappeared. The capital of Swabian hegemony was present-day Braga, but some Swabian kings lived in the Roman city of Cale (present-day Porto) at the mouth of the Douro River. The city was a customs post between Galicia and Lusitania. Gradually, the city came to be called Portucale, a compound of portus (port) and Cale. This name also referred to the vast territory to the immediate north and south of the banks of the river upstream from the city.

With large parts of the peninsula now outside their control, the Romans commissioned the Visigoths, the most highly Romanized of the Germanic peoples, to restore Rome's hegemony in 415. The Visigoths forced the Vandals to sail for North Africa and defeated the Swabians. The Swabian kings and their Visigothic overlords held commissions to govern in the name of the emperor their kingdoms were thus part of the Roman Empire. Latin remained the language of government and commerce. The Visigoths, who had been converted to Christianity in the fifth century, decided to organize themselves into an independent kingdom with their capital at Toledo. The kingdom was based on the principle of absolute monarchy, each sovereign being elected by an assembly of nobles. Visigothic kings convoked great councils made up of bishops and nobles to assist in deciding ecclesiastical and civil matters. Visigoths gradually fused with the Swabians and Hispano-Romans into a single politico-religious entity that lasted until the eighth century, when the Iberian Peninsula fell under Muslim domination.

Data as of January 1993