Irwin C. "Gunny" Gunsalus (June 29, 1912 – October 25, 2008) was an American biochemist who discovered lipoic acid, a vitamin-like substance (an enzyme cofactor) that has been used as a treatment for chronic liver disease, and pyridoxal phosphate, one of the active forms of vitamin B6.

In his role as assistant secretary general at the United Nations, he led the international body's research on genetic engineering.

[3] In 1950, he took a faculty position as professor of microbiology at the University of Illinois at Urbana-Champaign, shifting his speciality in 1955 to head the biochemistry department until 1966.

[2] While there, he co-authored The Bacteria: A Treatise on Structure and Function with Roger Y. Stanier, a five-volume work that served as a basic textbook for scientists entering the field.

[1] He also researched the way that soil microbes exchange plasmids, giving the organisms the ability to adapt to differing nutritional substances available in their environment.

Gunsalus was a postdoctoral advisor to Ananda Mohan Chakrabarty, who later used genetic engineering techniques for plasmid transfer to create microbes that could digest petroleum.