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.