A civil marriage is a marriage performed, recorded, and recognized by a government official. Such a marriage may be performed by a religious body and recognized by the state, or it may be entirely secular, in which it is known as a secular marriage.

Countries maintaining a population registry of its residents keep track of marital status, and all United Nations (UN) member states except Iran, Somalia, South Sudan, Sudan, and Tonga have signed or ratified either the United Nations Convention on Consent to Marriage, Minimum Age for Marriage, and Registration of Marriages (1962) or the United Nations Convention on the Elimination of All Forms of Discrimination against Women (1979) which carry a responsibility to register marriages. Most countries define the conditions of civil marriage separately from religious requirements. Certain states, such as Israel, allow couples to register only on the condition that they have first been married in a religious ceremony recognized by the state, or were married in a different country.

In medieval Europe, marriage was governed by canon law, which recognized only those marriages where the parties stated they took one another as husband and wife as valid, regardless of the presence or absence of witnesses. It was not necessary, however, to be married by any official or cleric. This institution was canceled in England with the enactment of the Marriage Act 1753, which required that, in order to be valid and registered, all marriages were to be performed in an official ceremony in a religious setting recognized by the state, i.e. Church of England, the Quakers, or in a Jewish ceremony. Any other form of marriage was abolished. Children born into unions that were not valid under the act would not automatically inherit the property or titles of their parents. For historical reasons, the act did not apply in Scotland. Consequently, until 1940, it continued to be enough in Scotland for a man and a woman to pledge their commitment to each other in front of witnesses to legalize their marriage. This led to an industry of "fast marriages" in Scottish towns on the border with England; the town of Gretna Green was particularly well known for this. The Marriage Act 1836 removed the requirement that the ceremony takes place in a religious forum, and registrars have given the authority to register marriages not conducted by a religious official.

Many European countries had institutions similar to common-law marriage. However, the Catholic Church forbade clandestine marriage at the Fourth Lateran Council (1215), which required all marriages to be announced in a church by a priest. In 1566, the edict of the Council of Trent was proclaimed denying Catholics any form of marriage not executed in a religious ceremony before a priest and two witnesses.

The Protestant pastor and theologian of Geneva, John Calvin, decreed that in order for a couple to be considered married they must be registered by the state in addition to a church ceremony.

In 1792, with the French Revolution, civil marriage was created in France and made independent from religious marriage which was no more recognised by the French state. In 1802, with the Organic Articles of the Concordat of 1801, Napoleon, advised by Portalis, in order to reconciliate civil and religious marriage in a state-controlled way, stated that religious ceremonies could be performed only for couples who had already been married in a civil ceremony [fr]. Napoleon spread this custom throughout most of Europe. In present-day France, only civil marriage has legal validity for the state. A religious ceremony may be performed only after the civil union, and it has no legal effect for the state. Since 1802 in France, religious ministers celebrating religious marriages without preliminary civil marriages risk criminal sanctions.

In Germany, the Napoleonic Code was valid only in territories conquered by Napoleon. With the fall of his empire, civil marriage in Germany began to die out. However, certain sovereign German states introduced civil marriages, which were either obligatory (like the French model) or optional, with either a religious or civil ceremony being accepted. Already before 1848, the Grand-Duchy of Saxe-Weimar-Eisenach enacted optional civil marriages, followed by the German republics of the Free City of Frankfurt upon Main (1850, obligatory), Free and Hanseatic City of Hamburg (1851, optional) and Free and Hanseatic City of Lübeck (1852, optional). German Grand-Duchies such as Oldenburg (1852/55, optional), Baden (1860), and Hesse (1860) as well as the Kingdom of Württemberg (1863) followed suit. Civil marriages enabled interfaith marriages as well as marriages between spouses of different Christian denominations. After the unification of Germany in 1871, the Reichstag adopted a bill initiated by Chancellor Otto von Bismarck as the "Civil Marriage Law" in 1875 (see: Kulturkampf); since then, only civil marriages have been recognized in Germany. Religious ceremonies may still be performed at the couple's discretion. Until December 31, 2008, religious marriages could not be performed until the couple had first married in a civil ceremony.

Today marriages in England or Wales must be held in authorized premises, which may include register offices, premises such as stately homes, castles, and hotels that have been approved by the local authority, churches or chapels of the Church of England or Church in Wales, and other churches and religious premises that have been registered by the registrar general for marriage.