Brčko District (Serbian, Bosnian, Croatian: Brčko Distrikt (Latin) Брчко Дистрикт (Cyrillic)) in northeastern Bosnia is a self-governing administrative unit under the sovereignty of Bosnia and Herzegovina; it is neither part of the Federation of Bosnia and Herzegovina nor Republika Srpska. The district remains under international supervision. The seat of the district is in the city of Brčko.
Brčko District was officially established on March 8, 2000, one year after an arbitration process; the process is viewed as violation of the Dayton Peace Accords because it created the district while it could only arbitrate the disputed portion of the Inter-Entity Boundary Line. The Brčko District was formed of the entire territory of the former Brčko municipality, of which 48% (including Brčko city) was in the Republika Srpska, while 52% was in the Federation of Bosnia and Herzegovina.
Before the war the Municipality of Brčko had 87,332 inhabitants (1991 census), 45% of whom were Muslims, 25% Croats, 21% Serbs, 6% Yugoslavs, and 3% others. After the war, the EU has maintained a diplomatic peace-keeping presence in the area.
According to the former mayor Branko Damjanac, the current population is composed of 40% Serbs, 39% Bosniaks, and 20% Croats. The Brčko District covers an area of 208 km² and has around 80,000 inhabitants.