The Lusitanians were an Indo-European-speaking people living in the far west of the Iberian Peninsula, in present-day central Portugal and 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).

Frontinus mentions Lusitanian leader Viriathus as the leader of the Celtiberians, in their war against the Romans. The Greco-Roman historian Diodorus Siculus likened them to another Celtic tribe: "Those who are called Lusitanians are the bravest of all similar to the Cimbri". The Lusitanians were also called Belitanians, according to the diviner Artemidorus. Strabo differentiated the Lusitanians from the Iberian tribes and thought of them as being Celtiberians who had been known as Oestriminis in ancient times. However, based on archeological findings, Lusitanians and Vettones seem to have been largely pre-Celtic Indo-European populations that adopted Celtic cultural elements by proximity. On the other hand, Pliny the Elder and Pomponius Mela distinguished the Lusitanians from neighboring Celtic groups like the Artabrians 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. Later, Gallaecia would become its own province (taking much of modern Galicia and Northern Portugal). 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.

Lusitanian mercenaries fought for Carthage between the years 218 and 201 BC, during the Second Punic War against Rome. Silius Italicus describes them as forming a combined with the Gallaeci and being led both by a commander named Viriathus (not to be confused with the similarly named chieftain). According to Livy, Lusitanian and Celtiberian cavalry performed raids in the north of Italy whenever the terrain was too rough for Hannibal's famed Numidian cavalry.

Since 193 BC, the Lusitanians had been fighting the Romans in Hispania. In 150 BC, they were defeated by Praetor Servius Galba: springing a treacherous trap, he killed 9,000 Lusitanians and later sold 20,000 more as slaves in Gaul (modern France). This massacre would not be forgotten by Viriathus, who three years later (147 BC) would become the leader of the Lusitanians, and severely damaged the Roman rule in Lusitania and beyond. In 139 BC, Viriathus was betrayed and killed in his sleep by three of his companions (who had been sent as emissaries to the Romans), Audax, Ditalcus and Minurus, bribed by Marcus Popillius Laenas (although they were Viriathus warrior companions they were not Lusitanians themselves, they seem to have been Turdetanians, or from other people that was not Lusitanian). However, when the three returned to receive their reward from the Romans, the Consul Quintus Servilius Caepio ordered their execution, declaring, "Rome does not pay traitors".

After the death of Viriathus, the Lusitanians kept fighting under the leadership of Tautalus, but gradually acquired Roman culture and language; the Lusitanian cities, in a manner similar to those of the rest of the Romanised Iberian peninsula, eventually gained the status of "Citizens of Rome".

Categorising Lusitanian culture generally, including the language, is proving difficult and contentious. 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 associated with the Beaker culture.

The Lusitanians worshiped various gods in a very diverse polytheism, using animal sacrifice. They represented their gods and warriors in rudimentary sculpture.

Endovelicus was the most important god for the Lusitanians. He is considered a possible Basque language loan god by some, yet according to scholars like José Leite de Vasconcelos, the word Endovellicus was originally Celtic, Andevellicos.

Endovelicus is compared with Welsh and Breton names, giving him the meaning of "Very Good God", the same epithet of the Irish god Dagda. Even the Romans worshiped him for his ability to protect. His cult eventually spread across the Iberian peninsula and beyond, to the rest of the Roman Empire and his cult was maintained until the fifth century; he was the god of public health and safety.

The goddess Ataegina was especially popular in the south; as the goddess of rebirth (spring), fertility, nature, and cure, she was identified with Proserpina during the Roman era.

Lusitanian mythology was heavily influenced by or related to Celtic mythology.

Also well attested in inscriptions are the names Bandua (one of the variants of Borvo) often with a second name linked to a locality such as Bandua Aetobrico, and Nabia, a goddess of rivers and streams.

According to Strabo the Lusitanians were given to offering sacrifices; they practiced divination on the sacrificial offering by inspecting its vitals and veins.

They also sacrificed human victims, prisoners of war, by striking them under coarse blankets and observing which way they fell. They cut off the right hands of their captives, which they offered to the gods.

The Lusitanian language was a Paleohispanic language that clearly belongs to the Indo-European family. The precise affiliation of the Lusitanian language inside the Indo-European family is still in debate: there are those who endorse that it is a para-Celtic language with an obvious Celticity to most of the lexicon, over many anthroponyms and toponyms. A second theory relates Lusitanian with the Italic languages; based on the names of Lusitanian deities with other grammatical elements of the area.

The Lusitanian language may in fact have been basal Italo-Celtic, a branch independent from Celtic and Italic, and splitting off early from Proto-Celtic and Proto-Italic populations who spread from Central Europe into western Europe after new Yamnaya migrations into the Danube Valley. Alternatively, a European branch of Indo-European dialects, termed "North-west Indo-European" and associated with the Beaker culture, may have been ancestral to not only Celtic and Italic, but also to Germanic and Balto-Slavic. Ellis Evans believes that Gallaecian - Lusitanian were one language (not separate languages) of the "P" Celtic variant.

The Lusitanians were a people formed by several tribes that lived between the rivers Douro and Tagus, in most of today's Beira and Estremadura regions of central Portugal, and some areas of the Extremadura region (Spain).

They were a tribal confederation, not a single political entity; each tribe had its own territory and was independent, and was formed by smaller clans. However, they had a cultural sense of unity and a common name for the tribes.

Each tribe was ruled by its own tribal aristocracy and chief. Many members of the Lusitanian tribal aristocracy were warriors as happened in many other pre-Roman peoples of the Iron Age.

Only when an external threat occurred did the different tribes politically unite, as happened at the time of the Roman conquest of their territory when Viriathus became the single leader of the Lusitanian tribes. Punicus, Caucenus and Caesarus were other important Lusitanian chiefs before the Roman conquest. They ruled the Lusitanians (before Viriathus) for some time, leading the tribes in the resistance against Roman attempts of conquest, and were successful.

The known Lusitanian tribes were:

• Arabrigenses
• Araocelenses
• Aravi
• Coilarni/Colarni
• Interamnienses
• Lancienses
  • Lancienses Oppidani
  • Lancienses Transcudani
  • Lancienses Ocelenses (may be the same as the Oppidani)
• Meidubrigenses
• Paesuri - Douro and Vouga (Portugal)
• Palanti (there is not agreement among scholars if they were Vettones or Lusitanian)
  • Calontienses
  • Caluri
  • Coerenses
• Petravioi
• Tangi
  • Elbocori
  • Igaeditani
  • Tapori/Tapoli - by the river Tagus, around the border area between Portugal and Spain
• Talures
• Veaminicori
• Vissaieici

It remains to be known if the Turduli Veteres, Turduli Oppidani, Turduli Bardili, and Turduli were Lusitanian tribes (coastal tribes), were related Celtic peoples, or were instead related to the Turdetani (Celtic, pre-Celtic Indo-European, or Iberians) and came from the south. The name Turduli Veteres (older or ancient Turduli), a tribe that dwelt in today's Aveiro District, seems to indicate they came from the north and not from the south (contrary to what is assumed on the map). Several Turduli peoples were possibly Callaeci tribes that initially came from the north, towards the south along the coast and then migrated inland along the Tagus and the Anas (Guadiana River) valleys.

If there were more Lusitanian tribes, their names are unknown.

The Lusitanians were considered by historians to be particularly adept at guerrilla warfare. The strongest amongst them were selected to defend the populace in mountainous sites. They used hooked javelins or saunions made of iron, and wielded swords and helmets like those of the Celtiberians. They threw their darts from some distance, yet often hit their marks and wounded their targets deeply. Being active and nimble warriors, they would pursue their enemies and decapitate them.

"In a narrow pass 300 Lusitani faced 1000 Romans; as a result of the action 70 of the former and 320 of the latter died. When the victorious Lusitani retired and dispersed confidently, one of them on foot became separated, and was surrounded by a detachment of pursuing cavalry. The lone warrior pierced the horse of one of the riders with his spear, and with a blow of his sword cut off the Roman’s head, producing such terror among the others that they prudently retired under his arrogant and contemptuous gaze."

— Orosius, Seven Books of History Against the Pagans, 5.4

In times of peace, they had a particular style of dancing, which required great agility and nimbleness of the legs and thighs. In times of war, they marched in time, until they were ready to charge the enemy.

Appian claims that when Praetor Brutus sacked Lusitania after Viriathus's death, the women fought valiantly next to their men as women warriors.

While the Lusitanians did not speak a Romance language, nowadays Lusitanian is often used as a metonym for the Portuguese people, and similarly Lusophone is used to refer to a Portuguese speaker within or outside Portugal, Brazil, Macau, Timor-Leste, Angola, Mozambique, Cape Verde, São Tomé and Príncipe, Guinea Bissau and others territories and countries.

• History of Portugal
• Timeline of Portuguese history
• Beira Alta
• Beira Baixa
• Ribatejo
• Alentejo
• Extremadura
• Emerita Augusta, capital of the Roman province of Lusitania (Lusitaniae et Vetoniae)
• Hispania
• Lusitania (Roman province)
• Pre-Roman peoples of the Iberian Peninsula
• List of Celtic tribes
• List of Celtic place names in Portugal
• List of Ancient Peoples of Portugal
• National Archaeology Museum (Portugal)
• Roman Empire
• Siege of the Blastophoenicians

• Detailed map of the Pre-Roman Peoples of Iberia (around 200 BC)
• Unknown ancient author text (about Julius Caesar in Hispania) of De Bello Hispaniensi (Spanish War).
• Pliny the Elder text of Naturalis Historia (Natural History), books 3-6 (Geography and Ethnography).
• Strabo's text of De Geographica ('About Geography').