Mayen-Koblenz is a district (Kreis) in the north of Rhineland-Palatinate, Germany. Neighboring districts are (from north clockwise) Ahrweiler, Neuwied, Westerwaldkreis, district-free Koblenz, Rhein-Lahn, Rhein-Hunsrück, Cochem-Zell, and Vulkaneifel.
The district was created in 1973 when the two districts, Mayen and Koblenz, were merged.
The two main rivers of the district are the Rhine and the Moselle, which join at the Deutsches Eck in Koblenz. In the west of the district are the Eifel mountains. These also include the large lake, the Laacher See, a volcanic caldera formed 12000 years ago.