Accreditation is a process of external quality review created and used by higher education to scrutinize colleges, universities, and programs for quality assurance and quality improvement. Accreditation in the United States is more than a hundred years old, emerging from concerns to protect public health and safety and to serve the public interest. It is carried out by private, nonprofit organizations designed for this specific purpose. External quality review of higher education is a nongovernmental enterprise. The U.S. accreditation structure is decentralized and complex, mirroring the decentralization and complexity of American higher education. This chapter provides an overview of self-regulation of higher education through accreditation, the primary means by which U.S. colleges and universities assure and improve academic quality.