Pre-Roman, Roman, Germanic, and Muslim periods
The earliest human remains found in Portugal are Neanderthal-type bones from Furninhas. A distinct culture first emerged in the Mesolithic (Middle Stone Age) middens of the lower Tagus valley, dated about 5500 bce. Neolithic (New Stone Age) cultures entered from Andalusia, leaving behind varied types of beehive huts and passage graves. Agriculture, pottery, and the working of soft metals followed by the same route. In the 1st millennium bce, Celtic peoples entered the peninsula via the Pyrenees, and many groups were projected westward by natural pressure. Phoenician and later Carthaginian influence reached southern Portugal in the same period. By 500 bce, Iron Age cultures predominated in the north. Celtic hilltop settlements (castros) retained their vitality after the Roman conquest.
After the Second Punic War (218–201 bce), Rome dominated the eastern and southern seaboards of the Iberian Peninsula, and Celtic peoples who had partially absorbed the indigenous population occupied the west. A Celtic federation, the Lusitani, resisted Roman penetration under the brilliant leadership of Viriathus; however, after Viriathus was assassinated about 140 bce, Decius Junius Brutus led a Roman force northward through central Portugal, crossed the Douro River, and subdued the Gallaeci. Julius Caesar governed the territory for a time. In 25 bce Caesar Augustus founded Augusta Emerita (Mérida) as the capital of Lusitania, which incorporated present-day central Portugal. Gallaecia (Galicia), to the north of the Douro, became a separate province under the Antonines. In Roman times the present-day districts of Beja and Évora formed a wheat belt. The valley of the Tagus was famous for its horses and farms, and there were important mines in the Alentejo. Notable Roman remains include the Temple of Diana at Évora and the site of Conimbriga (Condeixa). Christianity reached Lusitania in the 3rd century and Galicia in the 4th.
After 406 ce, foreign invaders forced their way into Gaul and crossed the Pyrenees. A Germanic tribe, the Suebi, settled in southern Galicia, and their rulers resided at or near Bracara Augusta (Braga) and Portucale. The Suebi annexed Lusitania and for a time overran the rest of the peninsula, but the Visigoths subdued them and extinguished their monarchy in 469. There are no records until about 550, when the Suebic monarchy had been restored and was reconverted to Catholicism by St. Martin of Braga. When Muslim forces invaded in 711, the only serious Gothic resistance was made at Mérida; upon its fall the northwest submitted. Berber troops were placed in central Portugal and Galicia. When ʿAbd al-Raḥmān I set up the Umayyad monarchy at Córdoba in 756, there was some resistance in the west; indeed, Lisbon was independent for a few years in the early 9th century. The restoration of the Christian sees of Galicia, the discovery of the supposed tomb of St. James, and the erection of his shrine at Santiago de Compostela (Santiago) were followed by the organization of the frontier territory of Portucale in 868 by Vimara Peres; Coimbra was annexed by the Christians but later was lost again.