The chapter presents a institutional theory. Institutional theory, a building block of today’s organization studies, drawing from sociology, social psychology, political science, and economics, offers explanations for social order, social action and cultural persistence. It does it with regard both to the stability of social systems at various levels (i.e. organization, field, society, world), and to the effects of institutional processes in situations of change or of conflicting legal, cultural or normative jurisdictions. Institutional theory highlights the role of rules, norms, and typifications (cultural beliefs and scripts) in constraining and empowering social action and giving meaning to social life. Earlier contributions emphasized the stabilizing role of institutions through the constitution of structures, organizational forms, fields and social actors’ identities. More recent contributions draw attention to the concurrent role of institutions in situations of change, where interests, agency and power play their own role in reaching stability or domination.