The 2004 UEFA European Football Championship, commonly referred to as Euro 2004, was the 12th edition of the UEFA European Championship, a quadrennial football competition contested by the men's national teams of UEFA member associations. The final tournament was hosted for the first time in Portugal, from 12 June to 4 July 2004. A total of 31 matches were played in ten venues across eight cities – Aveiro, Braga, Coimbra, Guimarães, Faro/Loulé, Leiria, Lisbon, and Porto.

The UEFA European Football Championship, less formally the European Championship and informally the Euro, is the primary association football tournament organised by the Union of European Football Associations (UEFA). The competition is contested by UEFA members' senior men's national teams, determining the continental champion of Europe. It is the second-most watched football tournament in the world after the FIFA World Cup; the Euro 2016 final was watched by a global audience of around 600 million. The competition has been held every four years since 1960, except for 2020, when it was postponed until 2021 due to the COVID-19 pandemic in Europe, but kept the name Euro 2020. Scheduled to be in the even-numbered year between FIFA World Cup tournaments, it was originally called the European Nations' Cup before changing to its current name in 1968. Since 1996, the individual events have been branded as "UEFA Euro [year]".