Fred Waldorf Stewart (Binghamton, 1894 – Sarasota, February 8, 1991) was an American surgical pathologist who was chief of pathology at Memorial Sloan-Kettering Cancer Center. Stewart was a friend of Cornelius P. Rhoads, who later became the director of Memorial Sloan-Kettering. Stewart, as "Ferdie," was the addressee of a controversial letter penned by Rhoads. Stewart also served as acting director of Memorial in 1944 while Rhoads was in the military. In 1947, while Rhoads was director of Memorial, Stewart received a grant of $30,000 for cancer pathology and other teaching. This was part of the largest aggregation of Federal cancer grants ever given to a single institution at that time, a total of $142,550.