Lennestadt lies in the Sauerland in southeast North Rhine-Westphalia and is a community in Olpe district. It is the district's most populous municipality. Lennestadt itself is not an actual town but a community which comprises several towns and villages.

The Sauerland is a rural, hilly area spreading across most of the south-eastern part of North Rhine-Westphalia, in parts heavily forested and, apart from the major valleys, sparsely inhabited.