The Treaty of Nice is a treaty adopted in Nice by the European Council to amend the two founding treaties of the European Union:

• the Treaty on European Union, or Maastricht Treaty, which introduced the euro and the three-pillar structure of the EU;
• the Treaty of Rome, which established the European Economic Community and the European Atomic Energy Community.
• It was agreed by the Heads of State or Government at the Nice European Council on 11 December 2000
• It was signed 26 February, 2001
• It came into force on 1 February 2003.