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.

[3] Mount Hayford, a 1,871 m mountain peak near Metlakatla, Alaska, United States, is named after him.

[4] A biography of Hayford may be found in the Biographical Memoirs of the National Academy of Sciences, 16 (5), 1935.