The Cologne Bonn Region (German: Region Köln/Bonn) is a metropolitan area in North Rhine-Westphalia (NRW), Germany, covering the cities of Cologne, Bonn and Leverkusen, as well as the districts of Rheinisch-Bergischer Kreis, Oberbergischer Kreis, Rhein-Erft-Kreis and Rhein-Sieg-Kreis.

The region covers an area of 3,839 km2 with 3.13 million inhabitants[1] (population density 815/km2).

Among the most prominent co-operative projects are the Cologne/Bonn Airport, the Verkehrsverbund Rhein-Sieg and the former Bonn–Cologne Railway Company.

The largest local banks, Sparkasse KölnBonn and Volksbank Köln Bonn, operate in both cities.

Since 2008, studies have been undertaken to incorporate cities of the Lower Rhine region (most notably the city of Düsseldorf) into the alliance, in order to form a Rhineland metropolitan region (Metropolregion Rheinland).