Patriarchy is a social system in which positions of dominance and privilege are primarily held by men. It is used, both as a technical anthropological term for families or clans controlled by the father or eldest male or group of males and in feminist theory where it is used to describe broad social structures in which men dominate over women and children. In these theories it is often extended to a variety of manifestations in which men have social privileges over others causing exploitation or oppression, such as through male dominance of moral authority and control of property. Patriarchal societies can be patrilineal or matrilineal, meaning that property and title are inherited by the male or female lineage respectively.

Patriarchy is associated various ideas forming patriarchal ideology that acts to explain and justify it and attributes it to inherent natural differences between men and women, divine commandment or other fixed structures. Sociologists hold varied opinions on whether patriarchy is a social product or an outcome of innate differences between the sexes. Sociobiologists compare human gender roles to sexed behavior in other primates and some argue that gender inequality comes primarily from genetic and reproductive differences between men and women. Social constructionists contest this argument, arguing that gender roles and gender inequity are instruments of power and have become social norms to maintain control over women.

Historically, patriarchy has manifested itself in the social, legal, political, religious, and economic organization of a range of different cultures. Most contemporary societies are, in practice, patriarchal.