Viriathus was the most important leader of the Lusitanian people that resisted Roman expansion into the regions of western Hispania or western Iberia, where the Roman province of Lusitania would be finally established after the conquest.

The Lusitanians were an Indo-European-speaking people living in the far west of the Iberian Peninsula, around roughly to Central Portugal and areas of modern-day Extremadura and Castilla y Leon of Spain. After its conquest by the Romans, the land was subsequently incorporated as a Roman province named after them (Lusitania).