Roger Yonchien Tsien (born February 1, 1952) is an American biochemist. He is a professor at the Department of Chemistry and Biochemistry, University of California, San Diego and was awarded the 2008 Nobel Prize in chemistry "for his discovery and development of the green fluorescent protein (GFP) with two other chemists: Martin Chalfie of Columbia University and Osamu Shimomura of Boston University and Marine Biological Laboratory.He received UCL Prize Lecture in Clinical Science in 2011.