Divorce or dissolution of marriage is the ending of a marriage before the death of either spouse, which can be contrasted with an annulment, which is a declaration that a marriage is void, though the effects of marriage may be recognized in such unions, such as spousal support, child custody and distribution of property.

In many developed countries, divorce rates have increased markedly during the twentieth century. Among the states in which divorce has become commonplace are the United States, South Korea and members of the European Union, with the exception of Malta (where all civil marriages are for life, because civil divorce is banned, which is also the case in the Philippines). In the USA, Canada, the United Kingdom and some other developed Commonwealth countries, this boom in divorce developed in the last half of the twentieth century. Japan retains a markedly lower divorce rate, though it has increased in recent years. In addition, acceptance of the single-parent family has resulted in many women deciding to have children outside marriage as there is little remaining social stigma attached to unwed mothers in some societies. The subject of divorce as a social phenomenon is an important research topic in sociology.

A divorce must be certified by a court of law, as a legal action is needed to dissolve the prior legal act of marriage. The terms of the divorce are also determined by the court, though they may take into account prenuptial agreements, or simply ratify terms that the spouses have agreed on privately. Often, however, the spouses disagree about the terms of the divorce, which can lead to stressful (and expensive) litigation. A less adversarial approach to divorce settlements has also emerged in recent years, known as family mediation, an attempt to negotiate mutually acceptable resolution to conflicts.