Where can I get a World of Warcraft authentication key?

In order to get a World of Warcraft authentication key, a player must first purchase the game. The game is available for purchase online and in many retail stores.

When a player purchases a retail version of the game, the authentication key is printed on the CD sleeve. If a player purchases the game from the Blizzard store online, the player can redeem it directly from the store or he can be provided with an authentication key to enter on his Battle.net account. Each authentication key can only be used for one Battle.net account, and players must purchase the base game before any of the expansions.