Lusitania, in ancient geography, the country of the Lusitani, and in a wider sense the name of one of the three provinces into which the Iberian peninsula was divided by Augustus. The Roman province occupied, like modern Portugal, the W. side of the peninsula, extending from Cape St. Vincent E. to the mouth of the Guadiana and N. to the Douro. It consequently did not include the N. provinces of Portugal, Minho and Tras os Montes. Eastward in the interior it extended far beyond the boundaries of Portugal, embracing the N. part of the old Spanish province of Estremadura and the S. part of Leon. The country of the Lusitani, however, was much smaller than the province to which its name was given. In this sense Lusitania included mainly the region between the Tagus and the Douro, from the Atlantic on the west to the present frontier of Portugal on the east. The province was anciently rich and fertile, and possessed valuable mines of gold and silver. Besides the Lusitanians, it contained several other tribes, of whom the most important were the Vettones, the Turduli Veteres, a branch of the Turdetani, and the Celtici, who were a remnant of the old Celtic population of the peninsula.

The chief city of Lusitania was Olisipo, the modern Lisbon, which was always a place of importance, though the Romans made Emerita Augusta, the modern Merida, the capital of their province. The Lusitani, according to Strabo, were the greatest nation of the peninsula, and the one most frequently and longest at war with the Romans. They were a brave and turbulent race, and much addicted to brigandage, especially those who dwelt among the mountains. They revolted in 153 B. C, and carried on for 14 years a gallant struggle against the Romans, who for a time were compelled to acknowledge their independence. Viriathus, who became their chief in 147, was finally assassinated by three of his own friends who had been bribed by the Romans, and the subjugation of the Lusitanians was soon afterward effected.