Colombier Castle, Medieval castle in Milvignes, Switzerland.

Colombier Castle stands on the foundations of a Roman villa from the 1st to 3rd century with preserved mosaics still visible. The building was expanded repeatedly from the 11th to 16th century and now forms a complex layout containing residential areas, museum galleries, and military barracks.

A Roman villa was built at this site between the 1st and 3rd century, establishing early settlement here. After the castle was built in the 11th century, the location evolved into an important regional fortress over the following centuries.

The castle's name comes from the Colombier family, lords of the site from the 11th century. In 938 it hosted the double wedding of Queen Bertha of Burgundy and her daughter Adelaide to Kings Hugh of Italy and Lothar. The bourg grew along today's rue du Château, the old road through the Roman villa linking the lake to the Vy d'Etra.

The castle stands on the north shore of Lake Neuchâtel, about 7 km from Neuchâtel. The site is an active federal army base (place d'armes since 1877), so access to the buildings is limited; the Roman remains and the castle exterior can be seen from the surrounding area. The bourg along the rue du Château, the old road linking the lake to the Vy d'Etra, gives the best approach on foot.

In 1840, workers digging a reservoir found old roof tiles and a column shaft, prompting archaeologist Frédéric Dubois de Montperreux (1798–1850) to begin the first excavations. His work revealed the scale of the Roman villa beneath the castle and raised awareness of the site's age among Neuchâtel residents.