The administrative act is the most common form of action taken by authorities. This work provides an overview of the entire historical development of this legal institution for the first time. It covers the period from the emergence of the administrative act in the 19th century to the present and offers a brief outlook on potential future developments regarding the internationalization of administrative law. Key focuses of the study include the formation of the definition of the administrative act, its legal foundations (priority and reservation of law), the development of legal force, and the possibilities for legal protection.