The Radolfzell–Mengen railway (also called in German the Hegau-Ablachtal-Bahn—Hegau–Ablach Valley Railway) is a branch line in the German state of Baden-Württemberg. It runs from Radolfzell via Stockach to Mengen. The line was built as a mainline connection from Ulm via Lake Constance (Bodensee) to Switzerland. Regular passenger services were abandoned between 1972 and 1982. Passenger services were reactivated on the southern section between Radolfzell and Stockach in 1996 and has since been operated under the brand name of Seehäsle. The northern section from Stockach to Mengen is however only used for freight trains and passenger excursion trains. In 2005, it had to be temporarily closed because of the deterioration of the infrastructure on some sections.