Yellapragada Subbarow (12 January 1895 – 9 August 1948) was an Indian biochemist who discovered the function of adenosine triphosphate as an energy source in the cell, and developed methotrexate for the treatment of cancer. Most of his career was spent in the United States. Despite his isolation of ATP, Subbarow was denied tenure at Harvard and remained without a green card throughout his life, though he would lead some of America's most important medical research during World War II.