The expansion pack World of Warcraft: Cataclysm sold through over 3.3 million units to customers in its first 24 hours of availability, Blizzard Entertainment said Monday.
The milestone -- which includes pre-orders -- marks the record for the fastest-selling PC game ever, the company said, citing internal records and data from distribution partners.
This latest expansion pack surpassed opening day sales of the November 2008 expansion Wrath of the Lich King, which sold 2.8 million copies in its first 24 hours of availability to capture the fastest-selling PC game record at the time.
The first WoW expansion, 2007's The Burning Crusade, sold nearly 2.4 million units in its opening day.
Cataclysm, which added new content and revamped the game's world of Azeroth to reflect a catastrophic event, launched in most regions on December 7, in Korea, Taiwan and Macau on December 9.
Originally launched in 2004, WoW currently has 12 million worldwide, according to Blizzard, making it the world's most popular subscription-based MMORPG.
Cataclysm is Blizzard's second major launch of 2010. "World of Warcraft: Cataclysm delivered even bigger day-one sales than we experienced with StarCraft II: Wings of Liberty in July," said Bob McKenzie, SVP of merchandising at GameStop.
The real-time strategy game StarCraft II sold 3 million units in its first month of release. Combined with Cataclysm's sales, "this a record year for Blizzard Entertainment at GameStop," McKenzie said.