The rule of law is declared to be a foundational and guiding value of the European Union in Article 2 Treaty on European Union. The European Commission claims to be the 'guardian of the rule of law', and the concept has been determinative in judgments in the Court of Justice of the EU. However, the EU has not defined what exactly is meant by 'the rule of law'. This leads to the question: how can the EU claim to be guided by the rule of law, 'common to all Member States', but not provide an account of what that means in practice? To determine such an account, I examine contemporary accounts of the rule of law and identify the specific nature of the EU. I conclude that while the rule of law is a shared value across legal systems, distinct accounts develop within, and adapt to, each one. I advance an EU-centric account of the rule of law (EUCA) which is apt for the EU legal order. I advocate the value of EUCA first in abstract by providing reasons for why it is to the benefit of the EU Institutions, the Member States and individuals to endorse EUCA compliance. I then show the practical use of EUCA as a source of legitimacy from the perspective of Member States and individuals in the context of issues of contemporary and pressing concern in the areas of international trade, corporate taxation and the criminal law. I seek to bridge the gap between a theoretical account of the rule of law apt for the EU legal order, and the practical guidance it can provide in the resolution of crisis issues. I conclude on the essential importance of guarding, strengthening, and enhancing the rule of law throughout the EU, not just as a means of resolution in times of crisis, but as a guarantee of the future of the European Union.