Arnold L. Demain (born 27 April 1927) is an American microbiologist. During his 60-year career, he has gained a renowned reputation in the field of industrial microbiology. He was formerly the Professor of Industrial Microbiology in the Biology Department at MIT and Founder and Head of Department of Fermentation Microbiology at Merck & Co. The August 2010 edition of The Journal of Antibiotics celebrated his scientific career.