John Mearsheimer is an American political scientist and international relations scholar, best known for his work on realism in global politics. He is a professor at the University of Chicago and has authored several influential books, including "The Tragedy of Great Power Politics," where he argues that great powers are inherently driven by competition and conflict. Mearsheimer is also known for his critique of U.S. foreign policy, particularly regarding NATO expansion and its impact on relations with Russia. His views have sparked significant debate among scholars and policymakers, making him a prominent figure in discussions about international security and strategy.