Kimberly Ellen Kagan (born 1972) is an American military historian and strategist, and the founder and president of the Institute for the Study of War (ISW), a non-profit think tank that provides independent research and analysis on military affairs, foreign policy, and national security. She earned a B.A. and Ph.D. in Classics from Yale University, where she later taught, and has also instructed at the United States Military Academy at West Point, Georgetown University, and American University. Her academic work spans ancient and modern military history, including studies of the Peloponnesian War and U.S. military operations.

Kagan is a prominent analyst and advocate of U.S. counterinsurgency strategies; she gained significant attention in 2009 when she joined General Stanley McChrystal’s strategic assessment team in Afghanistan. She frequently publishes op-eds in major outlets including The Wall Street Journal, The New York Times, and The Weekly Standard, and has been influential in public and policy discourse on national security. Her work has been associated with neoconservative perspectives that emphasize robust U.S. military engagement abroad, and she has faced criticism for her advocacy of the 2007 Iraq surge strategy.

She is married to fellow military historian Frederick Kagan, a senior fellow at ISW, and is related through marriage to commentator Robert Kagan.