JoAnne Stubbe (born June 11, 1946) is an American chemist best known for her work on ribonucleotide reductases, for which she was awarded the National Medal of Science in 2009.

[2] After she received her Ph.D. degree in organic chemistry under the guidance of Professor George Kenyon[2] from the University of California, Berkeley, in 1971, she did a very brief stint (1971–1972) as a postdoc at UCLA, where she worked on synthesizing LSD from tryptophan with Julius Rebek.

[5] Her first two publications in scientific journals showed the mechanisms for reactions that involved the enzymes enolase that metabolizes carbohydrates, and pyruvate kinase.

[5] Stubbe pioneered the use of spectroscopic investigations of enzyme interactions[10] and has devoted most of her career to elucidating the biochemical mechanisms behind free radicals.

In her early work at Yale and then at the University of Wisconsin, Stubbe discovered how enzymes called ribonucleotide reductases use free-radical chemistry to convert nucleotides into deoxynucleotides, an essential process in DNA repair and replication.

[4] Stubbe, in collaboration with John Kozarich, also elucidated the structure and function of bleomycin, an antibiotic that is commonly used to treat cancer.

[12] Stubbe's other research interests included the design of so-called suicide inhibitors and mechanisms of DNA repair enzymes.