The consummation of a marriage, or simply consummation, is the first officially credited act of sexual intercourse following marriage. In many traditions and statutes of civil or religious law, the definition usually refers to penile–vaginal penetration (i.e., heterosexual), and some religious doctrines hold an additional requirement prohibiting contraception. In this sense, "a marriage is consummated only if the conjugal act performed deposits semen in the vagina."

The religious, cultural, or legal significance of consummation may arise from theories of marriage as having the purpose of producing legally recognized descendants of both partners, or of providing sanction to their sexual acts together, or both, and its absence may amount to treating a marriage ceremony as falling short of completing the state of being married, or as creating a marriage which may later be repudiated. Thus, in some legal systems, a marriage may be annulled if it has not been consummated. Consummation is also relevant in the case of a common-law marriage. The historical importance of consummation has resulted in the development of various bedding rituals.

In addition to these formal and literal usages, the term also exists in informal and less precise usage to refer to a sexual landmark in relationships of varying intensity and duration.

The relevance of consummation in a civil marriage varies by jurisdiction. For example, under section 12 of the Matrimonial Causes Act 1973, a refusal or inability to consummate a marriage is a ground of annulment in England and Wales, but this only applies to heterosexual marriage because Paragraph 4 of schedule 4 of the Marriage (Same Sex Couples) Act 2013 specifically excludes non-consummation as a ground for the annulment of a same-sex marriage. Other common law jurisdictions, such as Australia, have abolished the legal concept of consummation.

In some countries, such as Egypt, Syria, Jordan, the United Arab Emirates, Saudi Arabia, Yemen, Libya, Mauritania, and Indonesia, religious marriage is the only legally binding marriage. In other countries, a religious marriage without civil registration may or may not be legally binding.

In the case of common law marriage, consummation may be a required component in the creation of the marriage itself.^{[citation needed]}

According to traditional Christian theological interpretations, "It is intended by God for the husband to be the one to break his wife's hymen", which when perforated during intercourse creates a blood covenant that seals the bond of holy matrimony between husband and wife. Consummation is particularly relevant in a Catholic marriage. Within the Catholic Church, if a matrimonial celebration takes place (ratification) but the spouses have not yet engaged in intercourse (consummation), then the marriage is said to be a marriage ratum sed non consummatum. Such a marriage, regardless of the reason for non-consummation, can be dissolved by the pope. Additionally, an inability or an intentional refusal to consummate the marriage is probable grounds for an annulment. Catholic canon law defines a marriage as consummated when the "spouses have performed between themselves in a human fashion a conjugal act which is suitable in itself for the procreation of offspring, to which marriage is ordered by its nature and by which the spouses become one flesh". Thus some theologians, such as Fr. John A. Hardon, S.J., state that intercourse with contraception does not consummate a marriage.

In many traditions, consummation is an important act because it suggests the bride's virginity; the presence of blood is erroneously taken as definitive confirmation that the woman was a virgin.