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 (according to their national procedures) of every single signatory.
Two core functional treaties, the Treaty on European Union (originally signed in Maastricht in 1992, The Maastricht Treaty) and the Treaty on the Functioning of the European Union (originally signed in Rome in 1957 as the Treaty establishing the European Economic Community i.e.