Leopold Ruzicka (September 13, 1887 - September 26, 1976) was a Nobel Prize winner in chemistry, the first one from Croatia. He holds eight honorary doctorates (4 Science, 2 Medicine, 1 Natural Sciences, 1 Law), 7 prizes and medals, and 24 honorary memberships in chemical, biochemical, and other scientific societies.

Leopold Ruzicka's first works originated during that period in the field of chemistry of natural compounds.
In 1916-1917, he received the support of the oldest perfume manufacturer in the world Haarman & Reimer, of Holzminden in Germany.
With expertise in the terpene field, he became senior lecturer in 1918, and in 1923, honorary professor at the ETH (Eidgenössische Technische Hochschule) as well the University in Zurich. Here, with a group of his doctoral students, he proved the structure and existence of the compounds of muscone and civet, the scents derived from the musk deer and the civet cat.
In 1921, the Geneva perfume manufacturers Chuit, Naef & Firmenich asked him to collaborate. Working here, Leopold Ruzicka achieved financial independence, but not as big as he did plan so he left Zurich to start working for the Ciba, Basle (Basel)- based company.
In 1927, he took over the organic chemistry chair at Utrecht University in Netherlands. In Netherlands he remained for three years, and then returned to Switzerland, which was superior in its chemical industry.
In 1939, he won the Nobel prize for chemistry with Adolf Butendandt.
In 1940, following the award, he was invited by the Croatian Chemical Association, where he delivered a lecture to an over packed hall of dignitaries. The topic of the lecture was From the Dalmatian insect powder to sex hormones.
During the World War II, some of his excellent collaborators were lost, but Leopold Ruzicka restructured his laboratory with new, younger and promising people; among them was young scientist Vladimir Prelog. With new people and ideas new research areas were opened. 
Following 1950, Leopold Ruzicka returned to chemistry, which had entered a new era of research. Now he turned to the field of biochemistry, the problems of evolution and genesis of life, particularly to the biogenesis of terpenes.
He published a hypothesis titled Biogenetic isoprene rule, which was the peak of his scientific career. Leopold Ruzicka retired in 1957, turning over the running of the laboratory to his assistant and future Nobel laureate Vladimir Prelog.