Marriage is a social union or legal contract between people that creates kinship. It is an institution in which interpersonal relationships, usually intimate and sexual, are acknowledged in a variety of ways, depending on the culture or subculture in which it is found. Such a union, often formalized via a wedding ceremony, may also be called matrimony.

People marry for many reasons, including one or more of the following: legal, social, emotional, economical, spiritual, and religious. These might include arranged marriages, family obligations, the legal establishment of a nuclear family unit, the legal protection of children and public declaration of commitment.

Marriage practices are very diverse across cultures, yet almost every known society has had some form of marriage between a man and a woman. In some societies an individual is limited to being in one such couple at a time (monogamy), while other cultures allow a male to have more than one wife (polygyny) or, less commonly, a female to have more than one husband (polyandry). Some societies also allow marriage between two males or two females. Societies frequently have other restrictions on marriage based on the ages of the participants, pre-existing kinship, and membership in religious or other social groups.

The act of marriage usually creates normative or legal obligations between the individuals involved. In some societies these obligations also extend to certain family members of the married persons. Almost all cultures that recognize marriage also recognize adultery as a violation of the terms of marriage, and forbid incestuous marriages. In cultures that allow the dissolution of a marriage this is known as divorce.

Marriage is usually recognized by the state, a religious authority, or both. It is often viewed as a contract. Civil marriage is the legal concept of marriage as a governmental institution irrespective of religious affiliation, in accordance with marriage laws of the jurisdiction. If recognized by the state, by the religion(s) to which the parties belong or by society in general, the act of marriage changes the personal and social status of the individuals who enter into it.