The diocese is located in the very west of Germany, extending from Krefeld in the north to the mountainous Eifel area in the south.

Bordering dioceses are Cologne, Münster, Essen and Trier in Germany, Liège in Belgium and Roermond in the Netherlands.

After the first bishop Marc Antoine Berdolet died in 1809, Pope Pius VII refused to commission the successor suggested by Napoleon, Jean Denis François Camus.

After the French rulership over the area, the diocese was abolished by the bull De salute animarum of July 16, 1821, and incorporated into the archdiocese of Cologne.

The principal church of the diocese is the Aachen Cathedral, of which the central part, the Palatine Chapel, was built in 800 under Charlemagne.