Rheindahlen is a town in the western and largest borough of the city of Mönchengladbach in the German state of North Rhine-Westphalia. Since the reorganisation of Monchengladbach's boroughs on 22 October 2009 Rheindahlen has been part of Mönchengladbach West. From the granting of Nideggen town rights in 1354 until the incorporation of the mayoralty of Rheindahlen into M.-Gladbach on 30 June 1921, the place was an independent town.
In 1878, the town was renamed from Dahlen to Rheindahlen in the Prussian Province of Düsseldorf by order of Emperor William I. Its renaming was primarily for postal reasons in order to avoid confusing the Dahlen in the Rhine Province with the municipality of Dahlen in Saxony within the North German Postal Zone. Its old name linguistically meant Delle or "hollow", which refers to the location of the village in a depression.