An oppidum (plural oppida) is a large fortified Iron Age settlement. Oppida are associated with the Celtic late La Tène culture, emerging during the 2nd and 1st centuries BC, spread across Europe, stretching from Britain and Iberia in the west to the edge of the Hungarian plain in the east. They continued to be used until the Romans conquered Southern and Western Europe. In regions north of the rivers Danube and Rhine, such as most of Germania, where the populations remained independent from Rome, oppida continued to be used into the 1st century AD.

Modern-day rendering of a Celtic Oppidum, Central Europe 1st century BC