Harold Boyd Woodruff (July 22, 1917 – January 19, 2017) was an American soil microbiologist. He was a member of the National Academy of Sciences. He was known for the discovery of actinomycin, and the development of the industrial production by fermentation of many natural products. This included cyanocobalamin (a synthetic form of Vitamin B12), the avermectins, and other important antibiotics.