This Element situates epistemic game theory at the intersection of decision theory, game theory, and interactive epistemology. It provides an overview and a critical assessment of some of the most classical results and contributions in the field: the epistemic characterization of Nash equilibrium, the epistemic interpretation of mixed actions, rationalizability in static games, and sub-game perfect equilibrium in dynamic games. The book furthermore discusses more recent contributions that highlight the importance of correlated beliefs in games, and as well as experimental and empirical findings on higher-order strategic reasoning.