Klaus D. Schmidt (born 1943) is an Austrian mathematician and retired professor at the Faculty of Mathematics, University of Vienna.After studying mathematics at the University of Vienna he received his doctorate in 1968 under Edmund Hlawka. He held visiting professorships in Technical University of Vienna, University of Manchester in 1969, Bedford College (1969-1974) and the University of Warwick from 1974 to 1994 after which he came back to the University of Vienna. He retired in 2009.