custom enjoining one to marry (marriage) within one's own group. The penalties for transgressing endogamous restrictions have varied greatly among cultures and have ranged from death to mild disapproval. When marriage to an outside group is mandated, it is referred to as exogamy.

Endogamy has been common among extant and historical aristocracies (aristocracy), religious groups (religion), ethnic groups (ethnic group), and social classes (social class). Expectations of caste endogamy persist in parts of India and the Indian diaspora, although many claim that this is a form of caste discrimination, a practice made illegal in the mid-20th century.