Patriarchy describes the structuring of society on the basis of family units, in which fathers have primary responsibility for the welfare of these units. In some cultures slaves were included as part of such households. The concept of patriarchy is often used, by extension, to refer to the expectation that men take primary responsibility for the welfare of the community as a whole, acting as representatives via public office (in anthropology and feminism, for example).

The feminine form of patriarchy is matriarchy, but there are no known examples of matriarchies from any point in history. Encyclopædia Britannica says it is a "hypothetical social system". The Britannica article goes on to note, "The view of matriarchy as constituting a stage of cultural development is now generally discredited. Furthermore, the consensus among modern anthropologists and sociologists is that a strictly matriarchal society never existed."

The anthropologist Margaret Mead said, "All the claims so glibly made about societies ruled by women are nonsense. We have no reason to believe that they ever existed. ... men everywhere have been in charge of running the show. ... men have been the leaders in public affairs and the final authorities at home." For moral comment on this see Feminist criticism below; for a scientific explanation of why, see Biology of gender below.