This text introduces the principles of noncooperative game theory -- including strategic form games, Nash equilibria, extensive-form games, subgame perfection, repeated games, and games of incomplete information -- in a direct and uncomplicated style that will acquaint students with the broad spectrum of the field while highlighting and explaining what they need to know at any given point. The analytic material is accompanied by many applications, examples, and exercises. Although game theory has been applied to many fields, Fudenberg and Tirole focus on the kinds of game theory that have been most useful in the study of economic problems. They also include some applications to political science. Game Theory can be used for a first or second course. It presents subgame perfection and Bayesian games with a minimum of detail with technical subtleties included in the advanced sections and uses markers to indicate the suitability of various sections to different audiences. The book is divided into five parts; static games of complete information, dynamic games of complete information, static games of incomplete information, dynamic games of incomplete information, and advanced topics.