John Fillmore Hayford (May 19, 1868 – March 10, 1925) was an eminent United States geodesist. His work involved the study of isostasy and the construction of a reference ellipsoid for approximating the figure of the Earth. Hayford was elected to the United States National Academy of Sciences in 1911 and the American Philosophical Society in 1915. The crater Hayford on the far side of the Moon is named after him. Mount Hayford, a 1,871 m mountain peak near Metlakatla, Alaska, United States, is named after him. A biography of Hayford may be found in the Biographical Memoirs of the National Academy of Sciences, 16 (5), 1935.