Treis-Karden is an Ortsgemeinde – a municipality belonging to a Verbandsgemeinde, a kind of collective municipality – in the Cochem-Zell district in Rhineland-Palatinate, Germany. It was the seat of the former like-named Verbandsgemeinde until 1 July 2014. Since then, it is part of the Verbandsgemeinde Cochem. Treis-Karden is a state-recognized tourism resort (Fremdenverkehrsort).
According to the latest research findings, Treis had its first documentary mention in 762 as trisgodros villa publica. The document in question is actually a 10th-century copy in Prüm Abbey’s Liber aureus. There were holdings at Treis owned by Polish queen Richeza, Count Palatine Ezzo's daughter, who apparently donated her property in 1051 and 1056 to the Brauweiler Monastery near Cologne. Beginning in the 11th century, Saint Castor's Foundation (Stift St. Kastor) in Karden had, by way of donations and purchases, important landholdings. In 1103, Ravengiersburg Monastery obtained by way of trade with St. Stephan in Mainz an estate in Treis (curtis in Tris). The name Karden is a modern form of the name for a Roman vicus, named in the latter half of the 5th century as Cardena by the geographer of Ravenna. In the late 6th century, Karden was the centre of a greater parish out of whose college of priests arose Saint Castor's Foundation in the 9th century. In 926, an exchange agreement contained the reference in Karadone, and in the 11th century, Karden was named as villa Cardiniacus
Saint Castor is held to have founded a Christian community in Karden as early as the 4th century. Castor's bones went in the 9th century mostly to Saint Castor's Church (Kastorkirche) in Koblenz. In antiquity and in the Middle Ages, Karden was a place of importance whose history was defined by the collegiate foundation that existed here until 1802. Karden was the centre of an archdeaconry. The foundation's provost was through personal union one of the five archdeacons of the Archbishopric of Trier.
Treis was the main centre of the Trechirgau. When this gau's counts, the Berthold-Bezeline family, died out in the late 11th century, it led to a whole series of disputes. For their part, the Counts of Salm-Rheineck sought to bring Treis along with its environs under their yoke. As early as 1121, Heinrich V destroyed the castle to support Count Palatine Gottfried von Calw. Apparently, Otto von Salm had only just had the castle newly built. In the struggle waged by Otto II von Rheineck (Otto von Salm's son) against Hermann von Stahleck over the Rhenish Electoral Palatinate, Treis eventually fell under Electoral-Trier lordship in 1148, remaining there until the late 18th century.
Beginning in 1794, both centres lay under French rule. In 1815 they were assigned to the Kingdom of Prussia at the Congress of Vienna. Since 1946, they have been part of the then newly founded state of Rhineland-Palatinate. On 7 June 1969, the two centres, until then each a separate municipality, were merged to form the new municipality of Treis-Karden.