The Administrative Procedure Act (APA), found in 5 U.S.C. §§ 551-559, is a foundational United States federal statute that governs the internal procedures of administrative agencies. It dictates how federal agencies may propose and establish regulations (rulemaking), and how they make decisions in individual cases (adjudication). It also establishes the framework for judicial review of agency actions, ensuring a check on their power. The APA is crucial for maintaining transparency, fairness, and public participation in the workings of the federal government.