Samuel Alfred Mitchell (April 29, 1874 – February 22, 1960) was a Canadian-American astronomer who studied solar eclipses and set up a program to use photographic techniques to determine the distance to stars at McCormick Observatory, where he served as the director.

Mitchell was awarded an astronomy assistantship for his second year at JHU and continued until he received his PhD in 1898 with his thesis published in the Astrophysical Journal, which included a discussion of the amount of astigmatism of a concave grating.

Following receipt of his doctoral degree, Mitchell set out for the brand new Yerkes Observatory in Wisconsin where he began work as a research student in 1898.

Mitchell became a world-renowned authority on solar eclipses through his numerous expeditions, including trips to: Sawah Loento, Sumatra in the Dutch East Indies (May 18, 1901), Daroca, Spain (August 30, 1905), Baker, Oregon (June 8, 1918), San Diego, California (September 10, 1923), Van Vleck Observatory, Middleton, Connecticut (January 24, 1925), Fagernas, Norway (June 29, 1927), Niuafoou or "Tin-Can" Island, Tonga, in the South Pacific Ocean (October 22, 1930), Magog, Quebec, Canada (August 31, 1932), and Kanton Island, Kiribati (June 8, 1937), this time as the scientific leader of a National Geographic Society Expedition.

On the 1918 Oregon and the 1925 Connecticut eclipses, Mitchell was accompanied by the artist Howard Russell Butler (1856–1934), whose paintings of totality graced the old Hayden Planetarium of the American Museum of Natural History for many years.

Mitchell spent much of his time and energy as director coming up with funds for running the observatory and paying staff and graduate students.

[1]: 258 The Mitchells' son, Allan (1902–1963), was chair of the Indiana University Physics Department from 1938 to 1963 and pioneered the creation of the IU Cyclotron Facility in 1941 (one of the first in the world).