Magna Carta (Latin for "Great Charter", literally "Great Paper"), also called Magna Carta Libertatum ("Great Charter of Freedoms"), is an English charter originally issued in 1215. Magna Carta was the most significant early influence on the extensive historical process that led to the rule of constitutional law today. Magna Carta influenced the development of the common law and many constitutional documents, such as the United States Constitution and Bill of Rights, and is considered one of the most important legal documents in the history of democracy.

Magna Carta was originally written because of disagreements among Pope Innocent III, King John and the English barons about the rights of the King. Magna Carta required the King to renounce certain rights, respect certain legal procedures and accept that his will could be bound by the law. It explicitly protected certain rights of the King's subjects, whether free or fettered — most notably the writ of habeas corpus, allowing appeal against unlawful imprisonment. Many clauses were renewed throughout the Middle Ages, and further during the Tudor and Stuart periods, and the 18th century. By the late 19th century, most clauses in their original form had been repealed from English law.

The Magna Carta was the first document which was forced onto an English King by his subjects in an attempt to limit his powers by law. (It was preceded by the 1100 Charter of Liberties in which King Henry I voluntarily stated what his own powers were under the law).

In practice Magna Carta mostly did not limit the power of the King in the Middle Ages; by the time of the English Civil War however it had become an important symbol for those who wished to show that the King was bound by the law.

Magna Carta is normally understood to refer to a single document, that of 1215. Various amended versions of the Magna Carta appeared in subsequent years however, and it is in fact the 1297 version which remains on the statute books of England and Wales.