Termantia, the present-day locality of Tiermes, is an archaeological site on the edge of the Duero valley in Spain. It is located in the sparsely populated municipio of Montejo de Tiermes.

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.