Magna Carta Libertatum (Medieval Latin for "Great Charter of Freedoms"), commonly called Magna Carta (also Magna Charta; "Great Charter"), is a royal charter of rights agreed to by King John of England at Runnymede, near Windsor, on 15 June 1215. First drafted by Archbishop of Canterbury, Cardinal Stephen Langton, to make peace between the unpopular king and a group of rebel barons, it promised the protection of church rights, protection for the barons from illegal imprisonment, access to swift justice, and limitations on feudal payments to the Crown, to be implemented through a council of 25 barons. Neither side stood behind their commitments, and the charter was annulled by Pope Innocent III, leading to the First Barons' War.

After John's death, the regency government of his young son, Henry III, reissued the document in 1216, stripped of some of its more radical content, in an unsuccessful bid to build political support for their cause. At the end of the war in 1217, it formed part of the peace treaty agreed at Lambeth, where the document acquired the name "Magna Carta", to distinguish it from the smaller Charter of the Forest which was issued at the same time. Short of funds, Henry reissued the charter again in 1225 in exchange for a grant of new taxes. His son, Edward I, repeated the exercise in 1297, this time confirming it as part of England's statute law. The charter became part of English political life and was typically renewed by each monarch in turn, although as time went by and the fledgling Parliament of England passed new laws, it lost some of its practical significance.

At the end of the 16th century, there was an upsurge in interest in Magna Carta. Lawyers and historians at the time believed that there was an ancient English constitution, going back to the days of the Anglo-Saxons, that protected individual English freedoms. They argued that the Norman invasion of 1066 had overthrown these rights, and that Magna Carta had been a popular attempt to restore them, making the charter an essential foundation for the contemporary powers of Parliament and legal principles such as habeas corpus. Although this historical account was badly flawed, jurists such as Sir Edward Coke used Magna Carta extensively in the early 17th century, arguing against the divine right of kings. Both James I and his son Charles I attempted to suppress the discussion of Magna Carta. The political myth of Magna Carta and its protection of ancient personal liberties persisted after the Glorious Revolution of 1688 until well into the 19th century. It influenced the early American colonists in the Thirteen Colonies and the formation of the United States Constitution, which became the supreme law of the land in the new republic of the United States. Research by Victorian historians showed that the original 1215 charter had concerned the medieval relationship between the monarch and the barons, rather than the rights of ordinary people, but the charter remained a powerful, iconic document, even after almost all of its content was repealed from the statute books in the 19th and 20th centuries. Three clauses (1, 9, and 29) remain in force in England and Wales.

Magna Carta still forms an important symbol of liberty today, often cited by politicians and campaigners, and is held in great respect by the British and American legal communities, Lord Denning describing it as "the greatest constitutional document of all timesthe foundation of the freedom of the individual against the arbitrary authority of the despot". In the 21st century, four exemplifications of the original 1215 charter remain in existence, two at the British Library, one at Lincoln Castle and one at Salisbury Cathedral. There are also a handful of the subsequent charters in public and private ownership, including copies of the 1297 charter in both the United States and Australia. Although scholars refer to the 63 numbered "clauses" of Magna Carta, this is a modern system of numbering, introduced by Sir William Blackstone in 1759; the original charter formed a single, long unbroken text. The four original 1215 charters were displayed together at the British Library for one day, 3 February 2015, to mark the 800th anniversary of Magna Carta.

John (24 December 1166 – 19 October 1216) was King of England from 1199 until his death in 1216. He lost the Duchy of Normandy and most of his other French lands to King Philip II of France, resulting in the collapse of the Angevin Empire and contributing to the subsequent growth in power of the French Capetian dynasty during the 13th century. The baronial revolt at the end of John's reign led to the sealing of Magna Carta, a document considered an early step in the evolution of the constitution of the United Kingdom.

John was the youngest of the four surviving sons of King Henry II of England and Duchess Eleanor of Aquitaine. He was nicknamed John Lackland because he was not expected to inherit significant lands. He became Henry's favourite child following the failed revolt of 1173–1174 by his brothers Henry the Young King, Richard, and Geoffrey against the King. John was appointed the Lord of Ireland in 1177 and given lands in England and on the continent. John unsuccessfully attempted a rebellion against the royal administrators of his brother, King Richard, whilst Richard was participating in the Third Crusade, but he was proclaimed king after Richard died in 1199. He came to an agreement with Philip II of France to recognise John's possession of the continental Angevin lands at the peace treaty of Le Goulet in 1200.

When war with France broke out again in 1202, John achieved early victories, but shortages of military resources and his treatment of Norman, Breton, and Anjou nobles resulted in the collapse of his empire in northern France in 1204. He spent much of the next decade attempting to regain these lands, raising huge revenues, reforming his armed forces and rebuilding continental alliances. His judicial reforms had a lasting effect on the English common law system, as well as providing an additional source of revenue. An argument with Pope Innocent III led to John's excommunication in 1209, a dispute he finally settled in 1213. John's attempt to defeat Philip in 1214 failed because of the French victory over John's allies at the battle of Bouvines. When he returned to England, John faced a rebellion by many of his barons, who were unhappy with his fiscal policies and his treatment of many of England's most powerful nobles. Although both John and the barons agreed to the Magna Carta peace treaty in 1215, neither side complied with its conditions. Civil war broke out shortly afterwards, with the barons aided by Louis VIII of France. It soon descended into a stalemate. John died of dysentery contracted whilst on campaign in eastern England during late 1216; supporters of his son Henry III went on to achieve victory over Louis and the rebel barons the following year.

Contemporary chroniclers were mostly critical of John's performance as king, and his reign has since been the subject of significant debate and periodic revision by historians from the 16th century onwards. Historian Jim Bradbury has summarised the current historical opinion of John's positive qualities, observing that John is today usually considered a "hard-working administrator, an able man, an able general". Nonetheless, modern historians agree that he also had many faults as king, including what historian Ralph Turner describes as "distasteful, even dangerous personality traits", such as pettiness, spitefulness, and cruelty. These negative qualities provided extensive material for fiction writers in the Victorian era, and John remains a recurring character within Western popular culture, primarily as a villain in films and stories depicting the Robin Hood legends.