Bak or BAK may refer to:
People Bak (surname), including a list of people with the name Bąk (surname), a Polish surname, including a list of people with the name Park (Korean surname), sometimes also Pak or Bak Bek (sculptor) or Bak, ancient Egyptian sculptor
Places Bäk, Lauenburg, Schleswig-Holstein, Germany Bak District, Khost, Afghanistan Bäk, Khost Province, Afghanistan Bak, Hungary Bak, South Khorasan, Iran Bąk (disambiguation), including several places in Poland
Science and technology Bak file, a filename extension commonly used to signify a backup copy Bill and keep, reciprocal payment in telecommunications systems Benzalkonium chloride, a cationic surfactant
Transport Battersea Park railway station, London, England, station code BAK Columbus Municipal Airport (Indiana), U.S., FAA airport code BAK BAK, IATA airport code for Baku metropolitan area, Azerbaijan
Other uses Bak (instrument), a Korean wooden clapper BAK (Austria), federal anti corruption agency BAK (magazine), online visual arts magazine Bashkir language, ISO 639 language code bak × Bakerara, abbreviation Bak., hybrid orchids BaK, World War I anti-balloon gun, from the German Ballonabwehrkanone Betrayal at Krondor, a video game Biking Across Kansas, an annual recreational and social rally Kocjan Bąk, a motor glider Lieutenant Bak, a character in novels by Lauren Haney
See also Bąk (disambiguation) Bcl-2 homologous antagonist killer, encoded by the BAK1 gene