Official Treaties are the foundations of the European Union and the primary source of EU law. Europa's European Treaties page provides an overview of the major treaties and includes links to explanatory texts for certain treaties (see lower-right corner of page).

The Founding Treaties

(Quotations taken from Europa's How the European Union Works)

Treaty Establishing the European Coal and Steel Community (ECSC)

Created the three "European Communities"--"the system of joint decision-making on coal, steel, nuclear power and other major sectors of the member states' economies." Established free trade area for many important economic and military resources.

Treaty on the Functioning of the European Union

Created a common market aimed at facilitating the movement of goods, services, capital, and labor. Abolished all internal tariffs. Established a common agricultural policy (CAP) and a common external trade policy.

Treaty Establishing the European Atomic Energy Community (Euratom)

Also signed in Rome--same dates as above Euratom was established to facilitate and encourage cooperation in atomic energy development and use.

Treaty on European Union (EU)

Established the European Union. Granted EU citizenship to every citizen of EU member states. Introduced central banking system and unified currency, the euro. "Introduced new forms of co-operation between the member state governments--for example on defence and in the area of 'justice and home affairs.' By adding this inter-governmental co-operation to the existing 'Community' system, the Maastricht Treaty created a new structure with three "pillars" which is political as well as economic. This is the European Union." Maastricht also renamed the EEC (created in the Treaty of Rome) to simply the EC--European Community--since the community's role had expanded beyond just economic concerns.

Treaty of Lisbon

The Treaty of Lisbon amends the Treaty on European Union and the Treaty Establishing the European Community. It increased the legislative and budgetary powers of the European Parliament, and created the function of President of the European Council.  The voting rules in the Council were also amended, calculating a double majority according to member states and according to EU population as a whole. The Treaty of Lisbon is also notable for containing the first explicit recognition of the right of a member state to leave the Union.

Other Treaties

(Quotations taken from Europa's How the European Union Works)

Single European Act (SEA)

Expanded scope of EEC. "Amended the EEC treaty and paved the way for completing the Single Market."

Treaty of Amsterdam

"Amended the EU and EC treaties, giving numbers (instead of letters) to the EU Treaty articles"

Treaty of Nice

"Further amends the other treaties, streamlining the EU's institutional system so it can continue to work effectively after a new wave of member states joins in 2004"

Treaties of Accession

The founding treaties are amended whenever new member states join the European Union. The most recent such amendment was in 2005, when Romania and Bulgaria were admitted to the EU. A complete list of the accession treaties is here.

The Treaties area of EUR-Lex contains the full text of all EU treaties, including

EUR-Lex also allows you to search treaties using keywords.