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 km with 3.13 million inhabitants (population density 815/km). The city centres of Cologne and Bonn are 24 kilometres apart. At the outer city limits, there are only eight kilometres between Cologne-Libur and Bonn-Geislar.
The Cologne/Bonn Region was established by local governments within the Cologne Government Region in 1992, to promote common policies in regional and urban planning, traffic management, environment and investment. Among the most prominent co-operative projects are the Cologne/Bonn Airport, the Verkehrsverbund Rhein-Sieg and the former Bonn–Cologne Railway Company. Also the Stadtbahn of both cities are connected, so there are light rail trains from Cologne Stadtbahn in Bonn and the Bonn Stadtbahn in Cologne. The largest local banks, Sparkasse KölnBonn and Volksbank Köln Bonn, operate in both cities. Both cities are directly connected by the autobahn A555.