TUN or tun may refer to:

Biology Tun shells, large sea snails of the family Tonnidae Tun, a tardigrade in its cryptobiotic state Tun or Toon, common name for trees of the genus Toona

Places Tun, Sweden, a locality in Västra Götaland County Tūn or Toon, the former name of Ferdows, a city in Iran Touro University Nevada, a private university in Henderson, Nevada, United States Tunisia, ISO 3166-1 alpha-3 country code Tunis–Carthage International Airport, (IATA airport code: TUN) Old English meaning town. Often used as a suffix in its Romanised form (~ton) e.g.: Southampton

Measurement and time Tun (Maya calendar), a unit of 360 days on the Maya calendar Tun (unit), an antiquated measurement of liquid

Science and technology TUN/TAP, a computer network device driver TUN (product standard), Danish building materials numbering system

Other uses Brilliance Tun, a 2014–2015 Chinese city car Tun, an honorific Malay title Tun, a type of cask (barrel) with a capacity of 252 wine gallons (954 litres) Lauter tun, a vessel used in brewing Mash tun, a vessel used in brewing

See also Ton (disambiguation)