Licensing, board certification, credentialing, and privileging constitute several complex regulatory systems. Decentralized state medical boards, federal agencies, accrediting bodies, and institutional medical staff offices seek to ensure that only qualified, competent practitioners are authorized to care for patients. This comprehensive review examines these regulatory requirements and core processes. Despite its centrality to patient safety and health care quality, the system is marked by significant fragmentation, administrative burden, inequity, and inefficiency.