John Allen is the name of a number of people, including:
- John Allen (Mississippi), a U.S. Representative from Mississippi
- John Allen (soldier), an American Army officer killed in the War of 1812
- John Allen (mayor), mayor of Rochester, New York in 1844
- John Allen (film), creator of the film Fallen
- John Allen (minister), an American minister who supported the American Revolution
- John Allen (university president), the first president of the University of South Florida, from 1960 to 1970
- John Allen (founder), a co-founder of the city of Ann Arbor, Michigan
- John B. Allen, the first U.S. Senator from Washington
- John F. Allen (physicist) (Jack Allen), a physicist who worked on superfluid helium
- John L. Allen, Jr., a reporter working for CNN and the National Catholic Reporter
- John W. Allen, an emeritus professor of physics at the University of St. Andrews, who has worked on electroluminescence and thermoluminescence of solids.
- John Whitby Allen, pioneering model railroader