The Aachen–Mönchengladbach railway is a main line in the German state of North Rhine-Westphalia. It is an important link between the Ruhr and Belgium for freight trains and is served by regional passenger trains. The line was built by the Aachen-Düsseldorf-Ruhrort Railway Company and is one of the oldest lines in Germany, which was opened between 1852 and 1854.

The Cologne–Aachen high-speed line is the German part of the Trans-European transport networks project high-speed line Paris–Brussels–Cologne. It is not a newly built railway line, but a project to upgrade the existing railway line which was opened in 1841 by the Rhenish Railway Company. When it was continued into Belgium in 1843, it became the world's first international railway line.