The Magna Carta, signed in 1215, is significant as it marked a pivotal moment in limiting the powers of the monarchy and laying the foundation for modern democracy. It established the principle that everyone, including the king, is subject to the law. This document influenced legal systems and constitutional developments worldwide, promoting ideas of individual rights, due process, and the necessity of consent in governance. The Magna Carta is often viewed as a cornerstone of English constitutional law and a precursor to many democratic principles still in use today.