Breisach (formerly Altbreisach) is a town with approximately 16,500 inhabitants, situated along the Rhine in the Rhine Valley, in the district Breisgau-Hochschwarzwald, Baden-Württemberg, Germany, about halfway between Freiburg and Colmar — 20 kilometres away from each — and about 60 kilometres north of Basel near the Kaiserstuhl. A bridge leads over the Rhine to Neuf-Brisach, Alsace.
Its name is Celtic and means breakwater. The root Breis can also be found in the French word briser meaning to break. The hill, on which Breisach came into existence was — at least when there was a flood — in the middle of the Rhine, until the Rhine was straightened by the engineer Johann Gottfried Tulla in the 19th century, thus breaking its surge.
The seat of a Celtic prince was at the hill on which Breisach is built. The Romans maintained an auxiliary castle on Mons Brisiacus (which came from the Celtic word Brisger which means waterbreak)
The Staufer founded Breisach as a city in today's sense. But there had already been a settlement with a church at the time. An 11th-century coin from Breisach was found in the Sandur hoard.
In the early 13th century, construction on the St Stephansmünster, the cathedral in Breisach, started. In the early 16th century, Breisach was a significant stronghold of the Holy Roman Empire