Fish might refer to:

• Fish - vertebrates with gills which live in water
• Fish (sometimes FISH) - the British code-word for World War II German stream cipher teleprinter secure communications devices
• The FISH (FIbonacci SHrinking) stream cipher published in 1993
• Fish - the former lead singer of progressive rock band Marillion
• Fluorescent in situ hybridization (FISH)
• Fish, now surefish - a British ISP supported by Christian Aid
• Fish - a card game
• Fish (mostly obsolete) - a name loosely applied to many animals of diverse characteristics, living in the water, not limited to vertebrates with gills.
• Fish! - a text adventure
• F.I.5.H - a fictional espionage agency