The document signed in 1215 to limit the powers of the English king was the Magna Carta. This landmark charter, signed by King John of England, established the principle that everyone, including the king, was subject to the law. It aimed to protect the rights of barons and limit arbitrary royal authority, setting a precedent for future legal and constitutional developments. The Magna Carta introduced ideas of due process and the rule of law, influencing later democratic frameworks and inspiring constitutional movements worldwide. Its legacy is celebrated as a foundational text in the history of individual rights and liberties.