Blizzard Entertainment, Inc. is an American video game developer and publisher based in Irvine, California, and a subsidiary of Activision Blizzard. Originally founded in 1991, the company is best known for producing the highly influential massively multiplayer online role-playing game World of Warcraft (2004), as well as the multi-million selling video game franchises Diablo, StarCraft and Overwatch. The company also operates Battle.net, an online gaming service.

Founded as Silicon & Synapse, Inc. by three graduates of the University of California, Los Angeles: Michael Morhaime, Frank Pearce and Allen Adham, the company began development of their own software in 1993, with games like Rock n' Roll Racing and The Lost Vikings, and changed its name to Chaos Studios, Inc. the same year, then to Blizzard Entertainment after being acquired by distributor Davidson & Associates in 1994; that year, the company released Warcraft: Orcs & Humans, which would receive numerous sequels and led to the highly popular World of Warcraft. By the end of the decade, Blizzard also found success with the action role-playing game Diablo (1997) and strategy game StarCraft (1998). The company became part of Vivendi Games in 1998, which would then merge with Activision in 2008, culminating in the inclusion of the Blizzard brand name in the title of the resulting holding company; Activision Blizzard became completely independent from Vivendi in 2013. Microsoft acquired Activision Blizzard in 2023, maintaining that the company will continue to operate as a separate business, while part of the larger Microsoft Gaming division; Blizzard Entertainment retains its function as the publisher of games developed by their studios.

Since 2005, Blizzard Entertainment has hosted annual gaming conventions for fans to meet and to promote their games, called BlizzCon, as well as a number of global events outside the United States. In the 2010s and 2020s, Blizzard has continued development of expansion packs for World of Warcraft (the most recent being 2024's The War Within), while also releasing StarCraft: Remastered (2017), Diablo III (2012) and Diablo IV (2023), as well as new material most notably the online multiplayer games Hearthstone, a collectible card game; Heroes of the Storm, a battle arena game; and Overwatch and Overwatch 2, which are first-person shooters. Since 2018, the company's reputation has suffered from a series of poorly received games, controversies involving players and staff, and allegations of sexual harassment and other misconduct against leading Blizzard employees.