X2

X2 may refer to:

Mathematics

* Square (algebra), also known as the "algebraic square", a concept in algebra
* Chi-square distribution, a theoretical probability distribution widely used in inferential statistics

Films

* "X2", a 2003 American movie also known as "X-Men United"
* "", also known as "X2" or "XXX²", a 2005 American film

Video games

* "X2", a video game
* "Final Fantasy X-2", a role-playing video game
* "Megaman X2", a platform game
* "", a space simulation game

Transportation craft

* Bell X-2, an experimental supersonic aircraft
* Sikorsky X2, a prototype, coaxial high-speed helicopter
* SpaceShipOne flight 17P, also known as "X2", the second Ansari X Prize flight
* Skycycle X-2, a rocket used by Evel Knievel
* HM Submarine X2, a Royal Navy submarine.
* Bathyscaphe "Trieste II", also known as "X-2", the US Navy bathyscaphe based on the "Trieste"
* X2 train, used for the X2000 train system in Sweden
* X2 (PWC), a personal water craft

Computer related

* X2 (protocol), a pre-V.90 standard for 56k downstream modem communications
* Athlon 64 X2, the first dual-core desktop CPU manufactured by AMD
* A two-lane PCI Express slot
* A type of 10 Gigabit Ethernet optical transceiver

Other

*X² (roller coaster), a Roller Coaster at Six Flags Magic Mountain
* Sendo X2, a Series 60 mobile phone
* The counterintelligence branch of the Office of Strategic Services, an American agency during World War II
* X-2 is the name of the fictional space shuttle series in the Epcot attraction,
* X-2 is the name of the Hydrofoil owned by the Venture family on the Venture Bros.