Leopold Ružička  (; born Lavoslav Stjepan Ružička; 13 September 1887 – 26 September 1976) was a Croatian-Swiss scientist and joint winner of the 1939 Nobel Prize in Chemistry "for his work on polymethylenes and higher terpenes" "including the first chemical synthesis of male sex hormones." He worked most of his life in Switzerland, and received eight doctorates honoris causa in science, medicine, and law; seven prizes and medals; and twenty-four honorary memberships in chemical, biochemical, and other scientific societies.