The milestone follows the November release of World of Warcraft's second expansion Wrath of the Lich King, which sold 4 million copies in its first month, 2.8 million of that in its first 24 hours of availability, making it the fastest-selling PC game of all time, according to Blizzard.

The previous record holder was the game's first expansion, The Burning Crusade, released in January 2007, selling some 2.4 million copies. World of Warcraft reached its 10 million subscribers milestone in January of this year, and surpassed 11 million subscribers in October.

The game is currently available in eight languages and in several territories, including North America, Europe, China, Korea, Australia, New Zealand, Singapore, Thailand, Malaysia, Chile, Argentina, Russia, Latin America, and the regions of Taiwan, Hong Kong, and Macau.

"We're pleased to welcome the new and returning players who have helped World of Warcraft reach these new milestones, and we appreciate the enthusiasm and support that the game's global community has continued to show," says Blizzard Entertainment CEO and co-founder Mike Morhaime. "We look forward to providing all of them with an excellent entertainment experience for a long time to come."

KeyWord: WoW,World of Warcraft,Blizzard,WoTLK