SMart Rhein-Ruhr e.V. is a German BDSM association, and by its own account one of the oldest and largest BDSM organisations in the German-speaking world, active for more than thirty years. It is a non-commercial, voluntary society rather than a business: it describes itself as working for the interests of people into BDSM, and as open to their partners and families and to anyone interested in the subject.

Its programme is a standing calendar rather than a series of one-off parties. It runs themed groups, regular Stammtische, outings, art and culture events, parties and workshops in many cities, mainly across the Rhine-Ruhr region — its own listings for September 2026 show recurring meetings in Essen, Bonn, Moers, Cologne and Bochum. It also publishes a map of its meeting points, thematic pages, an archive, a membership scheme and a section on its participation in Christopher Street Day.

It holds no premises of its own and gives no street address: contact runs through a telephone line answered by two named volunteers, mailing lists, a Telegram group and a post-office box. Membership is open and the site carries its own board and contact pages.