Definitions of and explanations for mental illness differ between societies and have changed over time. Current use of the term arises from secular and materialist epistemologies of the body and mind, influential from the 18th century, which rejected the spiritual or supernatural as causes of illness. Since the 19th century, a specialist body of study, of law, practices, professionals, and institutions developed to investigate, define, diagnose, and treat disorders and illnesses of the mind. This was the emergence of psychiatry and of a professional psychiatric sector. With origins in the West, at a time of capitalism and imperialism, psychiatry was brought to South Africa through colonialism, and its development has been strongly influenced by the country’s economic, political, ideological, and medico-scientific histories. There have been significant continuities: the sector has always been small, underfunded, and prioritized white men. Black patients were largely neglected. Discrimination and segregation were constant features, but it is helpful to identify three broad phases of the history of the psychiatric sector in South Africa. First, its most formative period was during colonial rule, notably from the mid-1800s to c. 1918, with an institutional base in asylums. The second broad phase lasted from the 1920s to the 1990s. A national network of mental hospitals was created and changes in the ways in which mental illnesses were classified occurred at the beginning of this period. Some new treatments were introduced in the 1930s and 1950s. Law and the profession’s theoretical orientations also changed somewhat in the 1940s, 1960s, and 1970s. Institutional practice remained largely unchanged, however. A third phase began in the 1980s when there were gradual shifts toward democratic governance and the progressive Mental Health Act of 2002, yet continued human rights violations in the case of the state duty of care toward the mentally ill and vulnerable.