Stefan Clessin (13 November 1833, in Würzburg – 21 December 1911, in Regensburg) was a German malacologist.[1]
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.[2][3] He conducted research of fossil mollusks as well as living species.[4]