Saint-Dizier (French pronunciation: [sɛ̃.di.zje]) is a subprefecture of the Haute-Marne department in north-eastern France.

However, far from any ocean or sea, Saint-Dizier experiences continental climate characteristics resulting in cold winters with freezing nights and cool days with temperatures staying in the single digits and warm to hot summers with frequent thunderstorms.

Named after an unknown saint (possibly Desiderius of Fontenelle), the town originated as a fortified settlement around a thirteenth-century château, eventually becoming a royal fortress to guard the French kingdom's eastern approaches.

The town was besieged and captured by Charles V, Holy Roman Emperor, in the summer of 1544.

The château was owned by the Orléans family until the French Revolution, was a base for German troops during World War II, and currently houses the Municipal Museum.