Over more than forty years, the European Union (formerly the European Community) has enacted a large number of directives aimed at harmonising company law rules across Member States. Nevertheless, differences across Member States persist with regard to company law rules. Member States’ regimes share a core of fundamental features: shareholders are not liable for the company's debts; companies have a separate legal personality; and the capital investment is commodified through the vehicle of freely disposable shares. Beyond these fundamental elements, it is more uncertain whether other general principles, having legal relevance, exist throughout the EU. By looking at national company law regimes and EU harmonising directives, this work has isolated only two principles that seem sufficiently general, common, and fundamental. The first principle is the unrestricted powers of directors to act on behalf of the company: this principle is based upon the German tradition and has been extended to public companies of all Member States by the First Company Law Directive of 1968. The second principle is equal treatment of shareholders who are in the same condition: this is a general duty that all companies’ bodies should respect when they make decisions that affect shareholders. Such a principle, however, is not a rigid equality rule, as differentiated treatment might still be justified in the interest of the company. However, its status within case-law of the European Court of Justice it is still unclear: on the one hand, the Court has denied that this duty is a general principle of EU law, with the consequence that it only applies within the scope of the specific provisions entailing this rule; on the other hand, other decisions of the Court seem to follow an opposite logic. Concerning insolvency law, it is much more controversial whether general principles exist within the EU legal order. Insolvency proceedings are country-specific, as most of their rules have a re-distributive impact on a broad range of stakeholders of the company, such as employees, creditors, and customers. Therefore, insolvency regimes are strictly related to political balances and national social security policies. The only common denominator of Member States insolvency regimes seems to be the duty to treat creditors equally and respect pre-insolvency entitlement and creditor ranking. Nevertheless, there is also an intricate web of exceptions to this principle, which vary broadly across jurisdictions and aim at protecting specific classes of creditors.