The Berlaymont building, or simply the Berlaymont (French pronunciation: [bɛʁlɛmɔ̃]), is an office building in Brussels, Belgium, which houses the headquarters of the European Commission, the executive branch of the European Union (EU). The structure is located on the Robert Schuman Roundabout at 200, rue de la Loi/Wetstraat, in the European Quarter. The unique form of the Berlaymont's architecture is used in the European Commission's official emblem. The building is named after the former Convent of the Ladies of Berlaymont [fr], which occupied the site.

The building has housed the European Commission since its construction, and has become a symbol of the European presence in Brussels and a metonym for the EU's executive power. The European Commission itself is spread over some 60-odd buildings, but the Berlaymont is the European Commission's headquarters, being the seat of the president of the European Commission and its College of Commissioners.

The following Directorates-General (departments) are also based in the Berlaymont: Human Resources and Security (HR), European Political Strategy Centre, formerly known as Bureau of European Policy Advisers (BEPA), Communication (COMM), Brussels Office of Infrastructure and Logistics (OIB), Secretariat-General (SG) and Legal Service (SJ).

The office of the president, the European Commission, and the boardroom, are on the 13th floor, together with the meeting room of the "Hebdo", as well as the restaurant La Convivialité.

Ursula von der Leyen is the first European Commission's president to actually reside in the Berlaymont. She sleeps in a small private area next to her main office on the 13th floor.

With the number of European civil servants rapidly growing since their arrival in Brussels in 1958, the Commission of the European Economic Community required progressively more office space across the city. By 1965, the EEC Commission alone had 3,200 staff scattered across eight different cramped buildings. The situation, which (due to the lack of large office blocks) began as soon as they arrived, became critical, and the EEC Commission tried to concentrate its staff in a number of rented buildings around the Robert Schuman Roundabout. The Belgian government, becoming aware of the problem and keen to ensure that the EEC Commission stayed, offered to build a prestigious administration complex large enough to house the entire staff. Walter Hallstein, President of the Commission of the European Economic Community, was interested but cautious about making long-term commitments while the issue of where the institutions were based was still being discussed. However, the need for office space was overwhelming.

The Belgian government's proposal required sufficient land, which would preferably be in the Leopold Quarter (where they were already based) and near the homes of the civil servants to the south and east. The land chosen was then occupied by the Convent of the Ladies of Berlaymont [fr], a 300-year-old convent that managed a girls' boarding school. The convent and school moved to a larger and quieter site in Waterloo, located south of today's Brussels-Capital Region. Once the Belgian state had finished their new school and built infrastructure for it, the Ladies of Berlaymont handed over the site — which, for years, they had been under pressure to sell to developers — to the Belgian government in November 1963.

To organise what was needed, the Belgian Foreign Minister Pierre Wigny suggested a Commission consultative Berlaymont, wherein the European Commission, the Belgian Public Works Ministry, the contractors and the architects could draw up the plans. However, the Belgian state desired not merely a building tailored to the European Commission, but one that could be used by its own civil servants were the European Commission to leave. This was also why the state favoured a central office building rather than the project for the construction of a "European city" in Etterbeek. The plans did not meet the exact desires of the European Commission, and hence the rent was reduced.