The Romans took over Carthage's territories in southern Spain when Scipio Africanus defeated the Carthaginians at the Battle of Ilipa in 207 BC during the Second Punic War. This area was turned into the Roman province of Hispania Ulterior (Further Spain). The Romans also annexed the area to its north, along the Mediterranean coast, where there were cities which were Roman allies. It became the Roman province of Hispania Citerior (Nearer Spain).

The conquest of the rest of Spain was very slow. There was fierce resistance by the Lusitanians, Celtiberians and other Iberian peoples which led to a number of wars

The First Celtiberian War (181 to 179 BC) was fought by the Celtiberians (Celtic-speaking peoples who lived in central, north-western and western Spain) led by the Lusones (a Celtiberian group) who resisted Roman advances from Hispania Citerior. The Romans won, redistributed land to the poor and signed separate peace treaties with the various Celtiberian peoples.

The Lusitanians, who lived in part of Portugal and part of Spain (in Extremadura and a small part of the province of Salamanca) resisted Roman advances from Hispania Ulterior. The first conflicts started in 194 BC and by 179 BC the Romans had pacified the region and signed a peace treaty. A major revolt, the Lusitanian War (155-139 BC) broke out. In 151 BC the Roman praetor Servius Sulpicius Galba subdued the rebels by treachery and massacred 10,000 people. This embittered the Lusitanian who continued their resistance. In 146 BC they started a successful guerrilla war. In 143 they allied with several Celtiberian groups. The war ended when the Lusitanian leader was murdered by three Lusitanians who had been bribed by the Romans

The Second Celtiberian War (154-152 BC) was fought by two Celtiberian groups, the Numantines (from the city of Numantia, in the north of present day Castile and Leon) and the Arevaci, who lived in the Meseta Central, a plateau in central Spain, next to Hispania Citerior. At the same time there was also war with the Lusitanians (see above). The Romans won all three conflicts. The Arevaci continued on and off armed resistance, sometimes in alliance with the Lusitanians. War flared up again in 143 in the Numantine War which lasted on an off until 133 when the Romans managed to capture the city, which was difficult to besiege. They forcibly disbanded the Celtiberian confederacy and granted the Pellendones and Uraci independence from the Arevaci. The Arevaci were absorbed into Hispania Citerior. They helped defending Celtiberian lands from invasion attempts by both the Lusitanians in 114 BC and the Cimbri, in 104-103 BC. Resentful that the Romans did not recognise their contribution, they rallied other disgruntled Celtiberians into ta revolt, the Third Celtiberian War(99-81 BC). The Romans defeated the Arevaci and destroyed their capital, Termantia, in 92 BC.

The conquest of north-western Spain (Cantabria, Asturias and León) occurred under the reign of Augustus with the Cantabrian or Cantabrian and Asturian Wars (29-19 BC).