Juliobriga (Spanish: Julióbriga, (Latin: Iuliobriga, Ancient Greek: Ἰουλιὃβριγα) was the most important urban centre in Roman Cantabria, as stated by numerous Latin authors including Pliny the Elder. The site has traditionally been identified with ruins in the village of Retortillo (Cantabria) and its Villafría district, in the municipality of Campoo de Enmedio.