A marriage license is a document

Document

The term document has multiple meanings in ordinary language and in scholarship. WordNet 3.1. lists four meanings :* document, written document, papers...

 issued, either by a church

Sacred Tradition

Sacred Tradition or Holy Tradition is a theological term used in some Christian traditions, primarily in the Roman Catholic, Anglican, Eastern Orthodox and Oriental Orthodox traditions, to refer to the fundamental basis of church authority....

 or state authority

Authority

The word Authority is derived mainly from the Latin word auctoritas, meaning invention, advice, opinion, influence, or command. In English, the word 'authority' can be used to mean power given by the state or by academic knowledge of an area .-Authority in Philosophy:In...

, authorizing a couple to marry

Marriage

Marriage is a social union or legal contract between people that creates kinship. It is an institution in which interpersonal relationships, usually intimate and sexual, are acknowledged in a variety of ways, depending on the culture or subculture in which it is found...

. The procedure for obtaining a license varies between countries and has changed over time. Marriage licenses began to be issued in the Middle Ages

Middle Ages

The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, to permit a marriage which would otherwise be illegal (for instance, if the necessary period of notice for the marriage had not been given).

Today, they are a legal requirement in some jurisdictions and may also serve as the record of the marriage itself, if signed by the couple and witnessed.

In other jurisdictions, a license is not required.