Tony Hawk's Underground 2 (also known as THUG 2 or Tony Hawk's Pro Skater 6) is the sixth installment in Neversoft's Tony Hawk's Series and is the sequel to 2003's Tony Hawk's Underground. Tony Hawk's Underground 2 was released on October 6, 2004 for the PlayStation 2, GameCube, Xbox, Windows, and Game Boy Advance platforms. It is also backwards compatible with the Xbox 360.

On March 18, 2005, it was released for the PlayStation Portable and renamed Tony Hawk's Underground 2 Remix.