The Patriarchy is part of feminist ideology. Broadly, feminists claim that men systematically oppress women. Some feminists group claim this oppression was done through the use of violence. Feminists vary on how long they believe The Patriarchy has existed. Some argue it has always existed while others argue it has only existed for a few thousand years and before that was the golden age of the ancient matriarchy.
MRAs and anti-feminists sometimes refer to Patriarchy theory. It is recommended to avoid this terminology as it gives far too much credence to The Patriarchy and feminists sometimes use the differing terminology to avoid having to justify their beliefs.
Claims concerning the existence of The Patriarchy posit the existence of a fundamental social division between men and women whereby men collectively rule society and hold all power over all women. At its most general The Patriarchy posits that (all) men have an interest in women’s oppression. The theory was conceived and developed by feminists during the second half of the twentieth century.
While they are often evasive on the topic, feminists broadly define Patriarchy as a society in which men systematically oppress women through the use of violence.
The English Wikipedia page for Patriarchy begins by defining Patriarchy in this manner:
Patriarchy is a social system in which men hold primary power and predominate in roles of political leadership, moral authority, social privilege and control of property.
This sentence is representative of feminist definitions and even without digging deeper it shows how deeply flawed the feminist notion of The Patriarchy is. Women have held greater moral authority in many societies including our own. Even more common has been the ability of women to move in the social hierarchy more easily then men, who often find themselves in a fixed position.
Sample Feminist Definitions
Patriarchy is the term used to describe the society in which we live today, characterised by current and historic unequal power relations between women and men whereby women are systematically disadvantaged and oppressed. This takes place across almost every sphere of life but is particularly noticeable in women’s under-representation in key state institutions, in decision-making positions and in employment and industry. Male violence against women is also a key feature of patriarchy. Women in minority groups face multiple oppressions in this society, as race, class and sexuality intersect with sexism for example. 
Patriarchy is a term used in feminism to describe the system of gender-based hierarchy in society which assigns most power to men, and assigns higher value to men, maleness, and "masculine traits". Feminism recognizes most of human society as patriarchal. Feminists work to end the perpetuation of patriarchy, deeming it oppressive for women and people of non-binary genders. Some feminists and anti-oppression activists prefer to analyse gendered power relations in terms of kyriarchy and/or intersectionality, finding "patriarchy" too focused on gendered societal power at the expense of other intersecting oppressions. Others prefer to continue using the term patriarchy when describing gendered oppression.
Patriarchal (adj.) describes a general structure in which men have power over women. Society (n.) is the entirety of relations of a community. A patriarchal society consists of a male-dominated power structure throughout organized society and in individual relationships.
In contrast, dictionary.com defines patriarchy like this:
pa·tri·arch·y [pey-tree-ahr-kee] Show IPA noun, plural pa·tri·arch·ies.
- a form of social organization in which the father is the supreme authority in the family, clan, or tribe and descent is reckoned in the male line, with the children belonging to the father's clan or tribe.
- a society, community, or country based on this social organization.
The feminist notion of The Patriarchy is unfalsifiable.
The Patriarchy, as defined by feminists, does not exist and never did exist. At best it is indicative of a very simplistic world view. At worst it is indicative of an ideological need to denigrate men and boys.
- Feminist Archeologist Accidentally Destroys Feminist Theory of Patriarchy
- Historical female leaders
- Ancient queens
- Female Rulers, Queens, Heads of State
- Ancient women rulers
- Female forms of power and the myth of male dominance
- Patriarchy:Feminist theory
- The Creation of Patriarchy, major feminist text on the topic
- Midwifing Death
- Feminism and Religion