World of Warcraft (WoW) is a massively multiplayer online role-playing game (MMORPG) released in 2004 by Blizzard Entertainment. It is the fourth released game set in the Warcraft fantasy universe. World of Warcraft takes place within the Warcraft world of Azeroth, approximately four years after the events at the conclusion of Blizzard's previous Warcraft release, Warcraft III: The Frozen Throne. Blizzard Entertainment announced World of Warcraft on September 2, 2001. The game was released on November 23, 2004, on the 10th anniversary of the Warcraft franchise.

The first expansion of the game, The Burning Crusade, was released on January 16, 2007. The second expansion, Wrath of the Lich King, was released on November 13, 2008. The third expansion, Cataclysm, was released on December 7, 2010. The fourth expansion, Mists of Pandaria, was released on September 25, 2012. The fifth expansion, Warlords of Draenor, was released on November 13, 2014. The sixth expansion, Legion, was released on August 30, 2016. The seventh expansion, announced on November 3, 2017, is Battle for Azeroth.

With a peak of 12 million subscriptions in October 2010 and Blizzard's final report of 5.5 million subscriptions in October 2015, World of Warcraft remains the world's most-subscribed MMORPG, and holds the Guinness World Record for the most popular MMORPG by subscribers. In January 2014, Blizzard announced that more than 100 million accounts had been created over the game's lifetime.

At BlizzCon 2017, Blizzard announced that it is developing a classic server option that provides a way to experience the game before any of its expansions launched.   - Wikipedia