X2 may refer to any of the following:
1. X2 is a modem transmission scheme developed by U. S. Robotics (3COM) that is capable of achieving line speeds up to 56 Kbps using schemes such as V.42bis. Because of the two conflicting standards of X2 and KFlex, a standard known as V.90 was developed to converge the two standards into a single, unified standard.
2. X2 is also sometimes an abbreviation used for the second generation of the Xbox.