Alonzo L. Hamby (born January 30, 1940) is an American historian and academic. He is distinguished professor of history emeritus at Ohio University and the recipient of two National Endowment for the Humanities Fellowships, a Harry S. Truman Library Institute Senior Fellowship, a Woodrow Wilson International Center for Scholars Fellowship, and the Ohio Academy of History Distinguished Service Award. He is an expert on Harry S. Truman and his presidency.