In many traditions and statutes of civil or religious law, the consummation of a marriage, often called simply consummation, is the first (or first officially credited) act of sexual intercourse between two people, following their marriage to each other. The definition of consummation usually refers to penile-vaginal sexual penetration, but some religious doctrines hold that there is an additional requirement that no contraception must be used.

The religious, cultural, or legal significance of consummation may arise from theories of marriage as having the purpose of producing legally recognized descendants of the 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 importance of consummation has led to 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.