International organizations with global or regional reach, such as the UN, IMF, World Bank, WTO, and EU, play an increasingly important role in the creation and implementation of international norms and rules, thus contributing to global governance. The security, economic well-being, protection of human rights, and ecological living conditions of people worldwide are influenced by the ability or inability of international organizations to facilitate and stabilize cooperation and governance beyond the nation-state. This textbook aims to inform readers theoretically and empirically about the conditions of emergence, development, functioning, and activities of international organizations. It introduces the key theories regarding international organizations and provides a historical overview.