Earl Charles Slipher (March 25, 1883 – August 7, 1964) was an American astronomer. He was the brother of astronomer Vesto Slipher.
Slipher was born in Mulberry, Indiana. He first joined Lowell Observatory in 1908 and became a noted planetary astronomer, concentrating on Mars. He published Photographic History of Mars (1905-1961). In 1957, he appeared in the "Mars and Beyond" episode of Disneyland discussing the possibility of life on Mars.
He also served as mayor of Flagstaff, Arizona from 1918 to 1920, and later as a member of the Arizona state legislature until 1933.
The crater Slipher on the Moon is named after Earl and Vesto Slipher, as is asteroid 1766 Slipher, discovered September 7, 1962, by the Indiana Asteroid Program.