Leland C. Clark Jr. (December 4, 1918 – September 25, 2005) was an American biochemist born in Rochester, New York.

[1] He is most well known as the inventor of the Clark electrode, a device used for measuring oxygen in blood, water and other liquids.

[2] Clark is considered the "father of biosensors", and the modern-day glucose sensor used daily by millions of diabetics is based on his research.

Clark began his professional career as an assistant professor of biochemistry at his alma mater, Antioch College, in Yellow Springs, Ohio.

From 1955 to 1958, he held a simultaneous appointment the University of Cincinnati College of Medicine as a Senior Research Associate in Pediatrics and Surgery.

Afterwards, he helped to found the company Synthetic Blood International, now known as Oxygen Biotherapeutics, Inc., which markets his invention Oxycyte.

Daniel Drake Award for Outstanding Achievements in Research, University of Cincinnati College of Medicine (1993).