Ulm, city, Baden-Württemberg Land (state), southwestern Germany. It lies on the left bank of the Danube River at its junction with the Iller and the Blau, opposite the Bavarian town of Neu Ulm. Ulm was first mentioned as a royal domain in 854 and was chartered in the 12th century by the Hohenstaufen emperors. It played a leading part in the town leagues and wars of the 14th and 15th centuries, becoming a free imperial city with extensive territorial authority.