- 1 January -
- Spain takes over the Presidency of the European Union.
- Euro notes and coins issued are in Austria, Belgium, France, Finland, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, Portugal and Spain.
- 15 January - Irish MEP Pat Cox is elected President of the European Parliament.
- 28 February - The Euro becomes the sole legal tender in all 12 Eurozone countries.
- 31 May - All 15 member nations of the European Union ratify the Kyoto Protocol, committing to an 8% cut in carbon dioxide emissions between 2008 and 2012 compared to 1990 levels.
- 1 July - Denmark takes over the Presidency of the European Union.
- 19 October - In a second referendum, the electorate of Ireland votes in favour of ratifying the Treaty of Nice.