Stefan Clessin

Stefan Clessin (13 November 1833, in Würzburg – 21 December 1911, in Regensburg) was a German malacologist.

He served as a military officer, and from 1862 worked for the Bavarian railways. He was an editor of the Malakozoologische Blätter and made major contributions to Martini and Chemitz' Systematisches Conchylien-Cabinet. He conducted research of fossil mollusks as well as living species.

Taxa described
Clessin named more than 90 species of non-marine gastropod mollusks, including:
 * Bythiospeum pfeifferi (Clessin, 1890)
 * Bythiospeum tschapecki (Clessin, 1882)