X², Steel roller coaster at Six Flags Magic Mountain, California.

X2 is a steel roller coaster at Six Flags Magic Mountain in Valencia, California, built by Arrow Dynamics as the prototype of its 4th Dimension design. Its 1,100-metre track runs on four rails: two carry the train, two control the seats, which rotate 360 degrees forward or backward independently of the chassis. The 3,610-foot layout has two raven turns, and the first drop of 215 feet is sloped at 88.5 degrees.

Arrow Dynamics developed this attraction as their final project before filing for bankruptcy in 2002, creating a new type of roller coaster. The installation received technical upgrades and a new name in 2008.

The name X2, adopted in 2008, refers to the second version of the ride; the original X opened in 2002 as the world's first fourth-dimension coaster. The 2007–2008 overhaul cost $10 million and added onboard audio, a tunnel and a light sequence, plus flame effects fired overhead as trains enter the outside raven turn. Designer Alan Schilke traced the concept to his childhood and the Zipper carnival ride.

Riders must be at least 1.22 m (48 in) tall. Each of the three trains has seven cars, with four riders per row seated in pairs on either side of the track. The ride closed permanently on September 29, 2026, so it can no longer be boarded.

Four rails guide the trains along the course while a rack and pinion system controls the rotation of the seats. Passengers can face forward or backward during the ride depending on the position of the seats at each moment.