The Xbox 360 and PlayStation 3 reinvention of the classic beat-em-up series made its debut in April 2011 courtesy of NetherRealm Studios, a new development team founded by Mortal Kombat creator Ed Boon.
NetherRealm's game takes the franchise back to its brutal roots, featuring robust 2D gameplay, a sophisticated fighting engine and some of the most gruesome moves yet seen in the notoriously bloodthirsty series.
Its character roster includes iconic combatants such as Scorpion, Sub Zero and Liu Kang, with God of War's Kratos making a guest appearance in the PlayStation 3 version.
Meanwhile, subsequent downloadable content has seen horror movie legend Freddy Krueger joining the fray.
The game has been met with critical acclaim and, having passed this latest sales milestone, now ranks as the top-selling fighting game of the year.
Mr Boon said: 'Fan reaction to this latest instalment has made all of our hard work worth it.'