Sidney Farber (September 30, 1903 – March 30, 1973) was an American pediatric pathologist. He is regarded as the father of modern chemotherapy for his work using folic acid antagonists to combat leukemia, which led to the development of other chemotherapeutic agents against other malignancies. Farber was also active in cancer research advocacy and fundraising, most notably through his establishment of the Jimmy Fund, a foundation dedicated to pediatric research in childhood cancers. The Dana–Farber Cancer Institute is named after him.