Bar-sur-Seine is a commune in the Aube department in north-central France. Situated on the River Seine, it is a rather quiet, pleasant, but run-down town just off the A5 autoroute. The town is famous for its castle, the Château de Bar sur Seine. The Ource forms part of the commune's southern border, then flows into the Seine, which flows northward through the middle of the commune.

The remains of the Château de Bar-sur-Seine are the ruins of a medieval French fortified castle, destroyed in the 16th century. The site is in the town of Bar-sur-Seine in the Aube département. The historic importance of the castle was due to its position on the frontier between Champagne (a vassal County of the King of France) and the Burgundy (a Duchy allied with the English) during the Hundred Years War. At the time, the Château de Bar sur Seine was considered the most important in Burgundy. Its architecture is close in style to that of the Château de Peyrepertuse in Aude.