Celtiberian or Northeastern Hispano-Celtic is an extinct Indo-European language of the Celtic branch spoken by the Celtiberians in an area of the Iberian Peninsula between the headwaters of the Douro, Tagus, Júcar and Turia rivers and the Ebro river. This language is directly attested in nearly 200 inscriptions dated from the 2nd century BC to the 1st century AD, mainly in Celtiberian script, a direct adaptation of the northeastern Iberian script, but also in the Latin alphabet. The longest extant Celtiberian inscriptions are those on three Botorrita plaques, bronze plaques from Botorrita near Zaragoza, dating to the early 1st century BC, labeled Botorrita I, III and IV.

The Indo-European languages are a language family native to the overwhelming majority of Europe, the Iranian plateau, and the northern Indian subcontinent. Some European languages of this family—English, French, Portuguese, Russian, Dutch, and Spanish—have expanded through colonialism in the modern period and are now spoken across several continents. The Indo-European family is divided into several branches or sub-families, of which there are eight groups with languages still alive today: Albanian, Armenian, Balto-Slavic, Celtic, Germanic, Hellenic, Indo-Iranian, and Italic; another nine subdivisions are now extinct.