BDO may refer to:

• BDO Global, the world's fifth-largest accountancy network
• Banco de Oro, one of the largest banks in the Philippines
• Barton, Durstine & Osborn, the former name of advertising agency BBDO
• Behavior Detection Officer
• Big Day Out, an annual music festival held in Australia and New Zealand
• Big Dumb Object, a term used in science fiction
• Black Desert Online, an MMORPG
• Block Development Officer, the official in charge of an administrative division (Block) of some South Asian countries
• British Darts Organisation (now defunct), former governing body of British darts
• Business Depot Ogden, the former Defense Depot Ogden Utah converted into a business park
• Husein Sastranegara International Airport, the IATA code served in Bandung, Indonesia
• Butanediol, especially 1,4-Butanediol, an organic chemical compound
• League of German Officers, German: Bund Deutscher Offiziere, an association of German prisoners of war in the Soviet Union