Attendorn is a city in the federal state of North Rhine-Westphalia with around 25,000 inhabitants. It is located in the southern Sauerland district "Kreis Olpe" and thus "in the middle of Germany". Attendorn is nationally known for its stalactite cave, the "Attahöhle" and the Bigge reservoir. Since 2012, Attendorn may officially bear the addition of Hanseatic City.

The nearest major centres are Siegen (45 kilometres), Hagen (60 kilometres), Dortmund (75 kilometres) and Cologne (85 kilometres).

The city is located in the Ebbegebirge nature reserve, just a few hundred metres north of the Bigge reservoir.

In the immediate vicinity, Attendorn borders the cities and municipalities of the districts Kreis Olpe and Märkischer Kreis. From the north and clockwise, these are Plettenberg, Finnentrop, Lennestadt, the district town Olpe, Drolshagen, Meinerzhagen and Herscheid.

In addition to the core town with almost 14,000 inhabitants, Attendorn comprises 55 further villages.