Ruzicka, Leopold (1887-1976) was a Croation-born Swiss chemist. He won the 1939 Nobel Prize in chemistry for his work on polymethylenes and higher terpenes, two kinds of hydrocarbons (organic compounds that contain only the elements hydrogen and carbon). Ruzicka shared the prize with the German chemist Adolph Friedrich Johann Butenandt, who independently studied sex hormones.

Ruzicka was born on Sept. 13, 1887, in Vukovar, Austria Hungary (now part of Croatia). In 1910, he received both an engineering diploma and a Ph.D. degree from the Technical University in Karlsruhe, Germany. He stayed on at the university as an assistant to his professor Hermann Staudinger. In October 1912, when Staudinger became director of the Federal Polytechnic Institute in Zurich, Switzerland, Ruzicka went with him. Together they studied natural chemicals used as insecticides.

With funding from a German perfume manufacturer, Ruzicka started his own research program in Zurich in 1916. In 1917, Ruzicka became a Swiss citizen and a lecturer at the Federal Polytechnic Institute. From 1918 to 1921, he conducted research for a Swiss chemical firm. In 1921, he began to work with higher terpenes. He discovered that certain terpenes consisted of large rings of carbon atoms. By understanding their structure, he was able to synthesize (produce artificially) some of these terpenes.

From 1926 to 1929, Ruzicka was professor of organic chemistry at the University of Utrecht in the Netherlands. He was director of the Federal Polytechnic Institute in Zurich from 1929 to 1957. In 1934, he synthesized testosterone, a male sex hormone.

Ruzicka died in Zurich on Sept. 26, 1976.