This work presents and analyzes the always relevant issue of agency, which exceptionally cannot be revoked by the principal. The systematic structure of previous editions is maintained in this version, and the content is enriched with the latest developments, particularly in the area of case law. Considering the importance of these changes and their identification by the scholar, especially the legal practitioner, in the context of temporal law, the latest developments are presented systematically and collected in separate paragraphs for immediate recognition, tracking, and understanding. The work consists of the Introduction, Part One and Part Two, and the Conclusions. The Introduction addresses the issue of irrevocable agency and includes a historical overview and comparative analysis. Following is the General Part, which covers the definition, prerequisites, lack of prerequisites, consequences, and termination of irrevocable agency. Particular emphasis is placed not only on analyzing the interests of the agent or third party that justify such a strong commitment but also on the specificity of the agency and the principal’s waiver of revocation. The relationship with the appointment of a sub-agent is also examined, and criticism is made of the prevailing opinion regarding the revocation of irrevocable agency due to a significant reason. In Part Two and the Special Section, specific forms appearing in practice are analyzed, such as in pre-contract agreements and in building construction with the system of conversion. Special importance is given to inheritable or posthumous irrevocable agency, whose validity has been questioned. The work concludes with extensive conclusions and detailed indexes.