This chapter introduces the field of international relations by discussing its key topics and theoretical approaches. It defines international relations as the study of interactions among various global actors including states, international organizations, NGOs, subnational groups and individuals. It outlines foundational questions in IR like the relationship between individuals and society, and between societies. It also discusses how history, philosophy and international relations theories can be used to analyze patterns in global events and state behavior. Finally, it contrasts major theoretical perspectives in IR like realism, liberalism, constructivism and radical theories.