Blackfish may refer to:
- Several of fish:
- Alaska blackfish, Dallia pectoralis.
- Black sea bass, Centropristis striata.
- Sacramento blackfish, Orthodon microlepidotus.
- Tautog, Tautoga onitis.
- Parore, Girella tricuspidata.
- Rudderfish, Centrolophus niger.
- Galjoen, Dichistius capensis.
- River blackfish, Gadopsis marmoratus, an Australian native freshwater fish.
- Japanese black porgy, Mylio macrocephalus, a large Japanese sea bream often cultivated in aquaculture
- Six cetaceans commonly called whales but classified scientifically in the Delphinidae or oceanic dolphin family:
- Melon-headed Whale, Peponocephala electra.
- Killer whale (Orca), Orcinus orca.
- Pygmy Killer Whale, Feresa attenuata.
- False Killer Whale, Pseudorca crassidens.
- Long-finned Pilot Whale, Globicephala melas.
- Short-finned Pilot Whale, Globicephala macrorhynchus.
- Chief Blackfish, a Shawnee leader of the 18th century.
- Brynden Tully, a character in George R.R. Martin's A song of Ice and Fire series
- Blackfish Software, a software company in the United States
- Blackfish, a SQL-92 compliant transactional multi-platform database
- Blakfish are an English math rock band who disbanded in 2010.