X3 may refer to:

Arts, entertainment, and media

Films

• X-Men: The Last Stand, also known as X3 and X-Men 3, the third film in the comic book film series
• XXX: Return of Xander Cage, a 2017 American film directed by D. J. Caruso

Literature and publications

• X3, a collection of three science fiction novellas by Gary A. Braunbeck

Music

• X3 (group), a short-lived Australian girl group, circa 2000
• X3 (album), a 2004 solo album by Japanese pop singer Aya Matsuura

Video games

• X-Men: The Official Game, a 2006 videogame prequel to X-Men: The Last Stand
• X³: Reunion, a space simulation computer game
  • X³: Terran Conflict, a sequel to X³: Reunion
    • X³: Albion Prelude, an addon to X³: Terran Conflict
• Dance Dance Revolution X3, a 2011 music video game by Konami
• Mega Man X3, a 1995 platforming game in Capcom's Mega Man X series

Electronics

Instruments

• Korg X3, a synthesizer

Phones

• Kyocera X3, an Android One smartphone by Kyocera
• Mobile phone models by Nokia
  • Nokia X3-00 or Nokia X3
  • Nokia X3 Touch and Type or Nokia X3-02

Sensors

• Foveon X3 sensor, a layered image sensor design

Mathematics, science, and technology

Astronomy

• Cygnus X-3, a binary x-ray source in the sky

Computer science

• X3, one former name of a subcommittee of ANSI, now International Committee for Information Technology Standards (INCITS)
• X3 (code) aka Excess-3, a binary code also termed Stibitz code
• XKO X3, an ERP software

Mathematics

• X³, the mathematical cubic function

Transportation

Aircraft

• Douglas X-3 Stiletto, an experimental jet aircraft
• Eurocopter X3, an experimental compound helicopter under development by Eurocopter

Automobiles

• Beijing X3, a Chinese subcompact crossover SUV
• BMW X3, a German compact SUV
• Cowin X3, a Chinese compact SUV
• Geely Vision X3, a Chinese subcompact crossover
• Jingyi X3, a Chinese subcompact crossover

Bus routes

• X3 (New York City bus)
• X3, a Metrobus route in Washington, D.C. U.S.

IATA codes

• TUI fly Deutschland (IATA airline designator X3 since 2007)
• Hapag-Lloyd Express (IATA airline designator X3, 2002-2007)

Motorcycles

• Ilmor X3 (also termed the X³), a MotoGP race motorbike

Spacecraft

• X-3, the Prospero (satellite) launched by the UK in 1971

Trains

• X3 (train), a Swedish train built by Alstom

Watercraft

• HMS X3, an X-class submarine of the Royal Navy

Graffiti

• X3(Suffix) is a common Gang tag Signature that is associated with the Mexican Mafia aka "La Eme" x3 is the notion of Roman Numeral 10 + 3 which is 13 for the Letter M; that is the thirteenth Letter of the Spanish and English Alphabets. Every allianced gang will include Some form or variant of the x3 or 13 in their Graffiti tagging.