Hindu caste of the Indian state of Kerala. Before the British conquest in 1792, the region contained small, feudal kingdoms, in each of which the royal and noble lineages, the militia, and most land managers were drawn from the Nāyars and related castes. During British rule, Nāyars became prominent in politics, government service, medicine, education, and law.

Unlike most Hindus, Nāyars traditionally were matrilineal. Their family unit, the members of which owned property jointly, included brothers and sisters, the latter's children, and their daughters' children. The oldest man was legal head of the group. Rules of marriage and residence varied somewhat between kingdoms.

Between the 16th and 18th centuries, Nāyars in the central kingdoms of Calicut, Walluvanad, Palghat, and Cochin had highly unusual marriage customs that have been much studied. Before puberty a girl ritually married a Nāyar or a Nambūdiri Brahman. The husband could visit her (but was not obliged to); in some cases ritual divorce immediately followed the ceremony. After puberty the girl or woman could receive a number of visiting husbands of her own or a higher caste. Nāyar men might visit as many women of appropriate rank as they chose. Women were maintained by their matrilineal groups, and fathers had no rights or obligations in regard to their children.

Early in the British period, Nāyar armies were disbanded. Perhaps partly as a result, plural marital unions gradually died out in the 19th century. Children began to be maintained by their father, to support him in his old age, and to perform the ceremonies at his death. Laws passed in the 1930s enforced monogamy, permitted division of the matrilineal estate among male and female members, and gave children full rights of maintenance and inheritance from the father. By the mid-20th century it was increasingly common, especially in towns, for nuclear families to form separate residential and economic units.