The Barroso Commission was the European Commission in office from 22 November 2004 until 31 October 2014. Its president was José Durão Barroso, who presided over 27 other commissioners (one from each of the states composing the European Union, aside from Portugal, which is Barroso's state). On 16 September 2009 Barroso was re-elected by the European Parliament for a further five years and his Commission was approved to take office on 9 February 2010.

Barroso was at first seen as the lowest common denominator by outside commentators, but his proposed team of Commissioners earned him some respect before triggering a crisis when the European Parliament objected to some of them, forcing a reshuffle. In 2007 the Commission gained two new members when Romania and Bulgaria joined the European Union.

Barroso's handling of his office was markedly more presidential than his predecessors. During his term the Commission passed major legislation including the REACH and 'Bolkestein' Directives. Under Barroso, the civil service in the Commission became more economically liberal.

Barroso was nominated as president and approved by Parliament in July 2004. However his proposed Commission met with opposition from the Parliament, notably concerning Rocco Buttiglione and his conservative comments which were seen as incompatible with his role as European Commissioner for Justice, Freedom and Security. The opposition plunged the EU into a minor crisis before Barroso conceded to the Parliament and reshuffled his team, removing Buttiglione, and his Commission took office on 22 November 2004. The commission was joined in 2007 by two further Commissioners when Bulgaria and Romania joined the EU.

The Prodi Commission was due to end its mandate at the end of October 2004, so following the 2004 elections to the Sixth European Parliament, candidates for Commission President began to be considered. There was strong backing for Belgian Prime Minister Guy Verhofstadt (EDLR) from Ireland, France and Germany who saw him as a "convinced European and also a fighter". However the federalist was opposed by Spain the United Kingdom, Italy and Poland due to his vocal opposition to both the Iraq War and the inclusion of God in the European Constitution. Irish Taoiseach Bertie Ahern (AEN) was also a popular candidate but did not wish to take up the job.

Due to the victory of the European People's Party in the previous election, EPP parties were keen to get one of their members into the post, including Luxembourgian Prime Minister Jean-Claude Juncker (EPP), who refused, and Austrian Chancellor Wolfgang Schüssel (EPP), who was in a coalition with the far-right Freedom Party of Austria which discredited him as a candidate to some governments.

A number of Commissioners were also touted, notably Franz Fischler, Commissioner for Agriculture (Austria, EPP), António Vitorino, Commissioner for JHA (Portugal, PES), Chris Patten, Commissioner for External Relations (UK, ED), Michel Barnier, and Commissioner for Regional Policy (France, EPP).

Other candidates were High Representative Javier Solana (Spain, PES) and President of the Parliament Pat Cox (Ireland, ELDR) however both were light candidates. However Barroso emerged as a leading candidate despite his support for the Iraq War and being seen as the lowest common denominator following objections to other candidates. The Parliament approved Barroso as president on 22 July 2004 by 413 votes to 215 (44 abstentions) with most of his support coming from the EPP-ED group. He did however earn praise for his later choice of commissioners.