The Treaty establishing a Constitution for Europe was an unratified international treaty intended to create a consolidated constitution for the European Union (EU). It would have replaced the existing European Union treaties with a single text, given legal force to the Charter of Fundamental Rights, and expanded qualified majority voting into policy areas which had previously been decided by unanimity among member states.

The Treaties of the European Union are a set of international treaties between the European Union (EU) member states which sets out the EU's constitutional basis. They establish the various EU institutions together with their remit, procedures and objectives. The EU can only act within the competences granted to it through these treaties and amendment to the treaties requires the agreement and ratification of every single signatory.