Marriage, also called matrimony or wedlock, is a culturally and often legally recognized union between people called spouses. It establishes rights and obligations between them, as well as between them and their children, and between them and their in-laws. It is nearly a cultural universal, but the definition of marriage varies between cultures and religions, and over time. Typically, it is an institution in which interpersonal relationships, usually sexual, are acknowledged or sanctioned. In some cultures, marriage is recommended or considered to be compulsory before pursuing any sexual activity. A marriage ceremony is called a wedding.

Individuals may marry for several reasons, including legal, social, libidinal, emotional, financial, spiritual, and religious purposes. Whom they marry may be influenced by gender, socially determined rules of incest, prescriptive marriage rules, parental choice, and individual desire. In some areas of the world, arranged marriage, child marriage, polygamy, and forced marriage are practiced. In other areas, such practices are outlawed to preserve women's rights or children's rights (both female and male) or as a result of international law. In some parts of the world, marriage has historically restricted the rights of women, who are (or were) considered the property of the husband. Around the world, primarily in developed democracies, there has been a general trend towards ensuring equal rights for women within marriage (including abolishing coverture, liberalizing divorce laws, and reforming reproductive and sexual rights) and legally recognizing the marriages of interfaith, interracial/interethnic/inter-caste, and same-sex couples. Controversies continue regarding the legal status of married women, leniency towards violence within marriage, customs such as dowry and bride price, forced marriage, marriageable age, and criminalization of premarital and extramarital sex. Female age at marriage has proven to be a strong indicator for female autonomy and is continuously used by economic history research.

Marriage can be recognized by a state, an organization, a religious authority, a tribal group, a local community, or peers. It is often viewed as a contract. A religious marriage is performed by a religious institution to recognize and create the rights and obligations intrinsic to matrimony in that religion. Religious marriage is known variously as sacramental marriage in Catholicism, nikah in Islam, nissuin in Judaism, and various other names in other faith traditions, each with their own constraints as to what constitutes, and who can enter into, a valid religious marriage.