Grady McWhiney (July 15, 1928 – April 18, 2006) was a historian of the American south and the U.S. Civil War.
McWhiney was born in Shreveport, Louisiana, and served in the Marine Corps in 1945. He married in 1947. He attended Centenary College on the G.I. Bill and earned an M.A. in history from Louisiana State University, working with Francis Butler Simkins. He received his Ph.D. in history from Columbia University in New York, working with David Herbert Donald.
McWhiney's dissertation dealt with Confederate General Braxton Bragg. McWhiney became a noted specialist on the American Civil War era, as well as southern social and economic history. He coauthored Attack and Die with his doctoral student Perry Jamieson. He published Braxton Bragg and Confederate Defeat, in two volumes, as well as many scholarly and popular articles and reviews. He lectured frequently to both academic and popular audiences.
McWhiney and Forrest McDonald were the authors of the "Celtic Thesis," which holds that most Southerners were of Celtic ancestry (as opposed to Anglo-Saxon), and that all groups he declared to be "Celtic" (Scots-Irish, Irish, Scottish, Welsh and Cornish) were descended from warlike herdsmen, in contrast to the peaceful farmers who predominated in England. They attempted to trace numerous ways in which the Celtic culture shaped social, economic and military behavior. For example, they demonstrated that livestock raising (especially of cattle and hogs) developed a more individualistic, militant society than tilling the soil.