Bob Cowley Riley (September 18, 1924 – February 16, 1994) was an American educator and politician who served as Acting Governor of Arkansas for 11 days in 1975. He had previously been a member of the Arkansas House of Representatives from 1946 to 1950, the mayor of Arkadelphia, Arkansas, in 1966 and 1967, and the eighth Lieutenant Governor of Arkansas from 1971 to 1975.