Bad Krozingen (German: [baːt ˈkʁɔtsɪŋən] ^ⓘ; Alemannic: Bad Chrotzige) is a spa town in the district Breisgau-Hochschwarzwald, in Baden-Württemberg, Germany. It is situated 15 km southwest of Freiburg. In the 1970s, the previously independent villages Biengen, Hausen an der Möhlin, Schlatt and Tunsel, including Schmidhofen, became part of Bad Krozingen.

Bad Krozingen is located in Breisgau, about 15 km southwest of Freiburg and 45 km north of Basel, surrounded by corn and tobacco fields. Together with Staufen the town forms a middle-order centre. The river Neumagen flows through the town, then into the Möhlin near Biengen, which flows into the Rhine at Breisach.

The neighbouring towns, clockwise from the north, include Breisach am Rhine, Munzigen, a district of Freiburg, Schallstadt, Ehrenkirchen, Staufen im Breisgau, Heitersheim, Eschbach and Hartheim.

The towns Biengen, Hausen an der Möhlin, Schlatt and Tunsel, which were independent until before the Community Reform in Baden-Württemberg in the 1970s, belong to Bad Krozingen. The four districts are localities in accordance with the municipal code of Baden-Württemberg, each having its own town council and a local mayor.

There are some finds (storage vessel and trapezoidal stone axe) which indicate that the area has been populated since the Neolithic. The Celts and Merovingians populated the area in the pre-Christian age and way past that. Open-field, river and place names, such as Neumagen, Möhlin, Kems, Tunsel, Belchen or Rhine, attest to that to the present day.

In the mid-1st century A.D. the Romans conquered the south-west of the present day area. Remains of a Roman road station, parts of pottery with kilns, a Roman fountain and foundations of several estates were founded in the following years. The Alemanni lived here from the 4th century. The oldest evidence of an Alemannic settlement includes graves at the former Roman road station and in the burial ground "Unterer Stollen" with 204 burials. Judging by the rich burial gifts, it was occupied between 500 and 700 A.D. Krozingen was mentioned for the first time in documents in the books of the monastery of St. Gallen as "Scrozzinga" in the year 808 A.D., probably named after the family of the Alemannic nobleman Crozzo. The town originated from the old center Oberkrozingen, Kems and Unterkrozingen as an Alemannic village at the junction of the Roman road Basel-Offenburg on the Neumagen.

Krozingen was part of the Breisgau district of Further Austria until it was transferred to the Electorate of Baden in Peace of Pressburg in 1805 and it had different overlords. Schnewlin von Landeck, the lords of Schauenburg and the lords of Pfirt are among these. The former Pfirt castle, where the lords had their seat and which currently is the Volksbank building, was named after them.

Thermal water was found in 1911 when searching for oil, which was thought to be present in Upper Rhine Plain. This finding was crucial to Krozingen as a future spa town. In 1933, after further drilling and starting a health spa business, Krozingen was given the title "Bad" (bath). A modern spa house was completed in 1959.