The Neckar is a river in Germany, a major tributary of the River Rhine, which it joins at Mannheim. Rising in the Black Forest, it flows through a steep valley in the Odenwald hills and passes through Tübingen, Nürtingen, Esslingen, Stuttgart, and Heidelberg. The total length of the Neckar from its source near Villingen-Schwenningen to the Rhine is 367 km. The Neckar is navigable for cargo ships up to the river port of Plochingen (about 200 km upstream from Mannheim).

The Neckar-Käpt’n fleet cruises upstream from Stuttgart to Plochingen, and downstream from Stuttgart to Heilbronn. The ships are used for day-trips only, as there are no cabins on board. But theorectically they could go further downstream to Mannheim, and further on the River Rhine to Basel or Rotterdam.