The Celtiberians were a group of Celts and Celticized peoples inhabiting an area in the central-northeastern Iberian Peninsula during the final centuries BC. They were explicitly mentioned as being Celts by several classic authors. These tribes spoke the Celtiberian language and wrote it by adapting the Iberian alphabet, in the form of the Celtiberian script. The numerous inscriptions that have been discovered, some of them extensive, have allowed scholars to classify the Celtiberian language as a Celtic language, one of the Hispano-Celtic languages that were spoken in pre-Roman and early Roman Iberia. Archaeologically, many elements link Celtiberians with Celts in Central Europe, but also show large differences with both the Hallstatt culture and La Tène culture.

The Celts or Celtic peoples were a collection of Indo-European peoples in Europe and Anatolia, identified by their use of Celtic languages and other cultural similarities. Major Celtic groups included the Gauls; the Celtiberians and Gallaeci of Iberia; the Britons, Picts, and Gaels of Britain and Ireland; the Boii; and the Galatians. The relation between ethnicity, language and culture in the Celtic world is unclear and debated; for example over the ways in which the Iron Age people of Britain and Ireland should be called Celts. In current scholarship, 'Celt' primarily refers to 'speakers of Celtic languages' rather than to a single ethnic group.