The king who signed the Magna Carta was King John of England. In 1215, faced with a revolt by his barons due to heavy taxation and arbitrary rule, King John reluctantly agreed to a series of guarantees, known as the Magna Carta. This document established the principle that the king was not above the law, laying the groundwork for modern democracy and the rule of law. The Magna Carta is often regarded as a foundational text in the development of constitutional limits on monarchical power, influencing subsequent legal and political systems in England and beyond.