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 fantasy Warcraft universe, which was first introduced by Warcraft: Orcs & Humans in 1994.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 set of the game, The Burning Crusade, was released on January 16, 2007.The second expansion set, Wrath of the Lich King, was released on November 13, 2008.The third expansion set, Cataclysm, was released on December 7, 2010. The fourth expansion set, Mists of Pandaria, was released on September 25, 2012.The fifth expansion set, Warlords of Draenor, was released on November 13, 2014.The sixth expansion set, Legion, was released on August 30, 2016.

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.

As with other MMORPGs, players control a character avatar within a game world in third- or first-person view, exploring the landscape, fighting various monsters, completing quests, and interacting with non-player characters (NPCs) or other players. Also similar to other MMORPGs, World of Warcraft requires the player to pay for a subscription, either by buying prepaid game cards for a selected amount of playing time or by using a credit or debit card to pay on a regular basis. Players may instead use a trial account that lets the player character reach level 20 for free but has many features locked.

To enter the game, the player must select a server, referred to in-game as a realm. Each realm acts as an individual copy of the game world and falls into one of four categories. Available realms types are:

    Normal – a player versus environment (PvE) realm where the gameplay is more focused on defeating monsters and completing quests, player-versus-player fights must be consensual, and any roleplay is optional.
    PvP – an environment where, in addition to defeating monsters and completing quests, open player-versus-player combat is the norm, and a player can be attacked by an opposing faction's player at any time.
    RP – a variant of PvE, where players roleplay in-character.
    RP-PvP – roleplay-PvP – a variant of PvP, where players are in-character and cross-faction combat is assumed.

Realms are also categorized by language, with in-game support in the language available.

Players can make new characters on all realms within the region, and it is also possible to move already established characters between realms for a fee.

To create a new character, in keeping with the storyline of previous Warcraft games, players must choose between the opposing factions of the Alliance or the Horde. Characters from the opposing factions can perform rudimentary communication (most often just "emotes"), but only members of the same faction can speak, mail, group, and join guilds. The player selects the new character's race, such as orcs or trolls for the Horde, or humans or dwarves for the Alliance.Players must select the class for the character, with choices such as mages, warriors, and priests available.Most classes are limited to particular races.