The Lusitanians (or Latin: Lusitani) were an Indo-European people living in the west of the Iberian Peninsula prior to its conquest by the Roman Republic and the subsequent incorporation of the territory into the Roman province of Lusitania (most of modern Portugal, Extremadura and a small part of the province of Salamanca).
Classical sources mention Lusitanian leader Viriathus as the leader of the Celtiberians, in their war against the Romans. The Greco-Roman historian Diodorus Siculus attributed them a name of a Germanic tribe: "Those who are called Lusitanians are the bravest of all Cimbri". The Lusitanians were also called Belitanians, according to the diviner Artemidorus.Strabo differentiated the Lusitanians from the Iberian tribes.Pliny the Elder and Pomponius Mela distinguished the Lusitanians from neighboring Celtic groups in their geographical writings.
The original Roman province of Lusitania briefly included the territories of Asturia and Gallaecia, but these were soon ceded to the jurisdiction of the Provincia Tarraconensis in the north, while the south remained the Provincia Lusitania et Vettones. After this, Lusitania's northern border was along the Douro River, while its eastern border passed through Salmantica and Caesarobriga to the Anas (Guadiana) river.
Categorising Lusitanian culture generally, including the language, is proving difficult. Some believe it was essentially a pre-Celtic Iberian culture with substantial Celtic influences, while others argue that it was an essentially Celtic culture with strong indigenous pre-Celtic influences.