Blizzard Entertainment, Inc. is an American video game developer and publisher based in Irvine, California. The company was founded in February 1991 as Silicon & Synapse, Inc. by three graduates of the University of California, Los Angeles: Michael Morhaime, Frank Pearce and Allen Adham. The company originally concentrated on the creation of game ports for other studios' games before beginning development of their own software in 1993, with games like Rock n' Roll Racing and The Lost Vikings. In 1993, the company became Chaos Studios, Inc.

In early 1994, they were acquired by distributor Davidson & Associates for $6.75 million ($13.3 million today). Shortly after this point, they were contacted by a Florida company, Chaos Technologies, who wanted the company to pay US$100,000 (equivalent to $197,441 in 2022) to keep the name. Not wanting to pay that sum, the executives decided to change the studio's name to "Ogre Studios" by April 1994. However, Davidson & Associates did not like this name, and forced the company to change it. According to Morhaime, Adham began running through a dictionary from the start, writing down any word that seemed interesting and passing it to the legal department to see if it had any complications. One of the first words they found to be interesting and cleared the legal check was "blizzard", leading them to change their name to "Blizzard Entertainment" by May 1994. Shortly thereafter, Blizzard Entertainment shipped their breakthrough hit Warcraft: Orcs & Humans, a real-time strategy (RTS) game in a high-fantasy setting.

In 1996, Blizzard Entertainment acquired Condor Games of San Mateo, California, which had been working on the action role-playing game (ARPG) Diablo for Blizzard at the time. Condor was renamed Blizzard North, with Blizzard's main headquarters in Irvine renamed to Blizzard South to distinguish the two. Diablo was released at the very start of 1997 alongside Battle.net, a matchmaking service for the game. Blizzard North developed the sequel Diablo II (2000), and its expansion pack Lord of Destruction (2001). Following these releases, a number of key staff from Blizzard North departed for other opportunities, such as Bill Roper. Blizzard's management made the decision August 2005 to consolidate Blizzard North into Blizzard South, relocating staff to the main Blizzard offices in Irvine, and subsequently dropping the "Blizzard South" name.

On February 21, 1996, CUC International announced its intention to acquire Davidson & Associates (including Blizzard Entertainment) and Sierra On-Line, two American video game companies, in a US$1.8 billion stock swap. The deal closed on July 24, 1996. Subsequently, following the acquisitions, CUC International established CUC Software (later known as Vivendi Universal Games) around the Torrance, California-based operations of Davidson & Associates to oversee the new video game properties.

On May 28, 1997, CUC International announced plans to merge with Hospitality Franchise Systems to create a single, "one-stop" entity. The merger was finalized in December that year and created Cendant. As a result of the merger, CUC Software was renamed Cendant Software.

On November 20, 1998, French media company Havas (acquired by Vivendi earlier that year) announced that it would acquire Cendant Software for $800 million in cash, with up to an additional $200 million contingent on its performance. Subsequently, the division was renamed Havas Interactive. On May 16, 2001, Havas Interactive was renamed Vivendi Universal Interactive Publishing, while Havas itself became Vivendi Universal Publishing. The new name was likely due to the merger between Universal and Vivendi; the company also received ownership of properties from Universal Interactive Studios. Under the new name, the company was split into two parts: Vivendi Universal Interactive Publishing North America and Vivendi Universal Interactive Publishing International, both of which took responsibility for their respective publishing regions. On November 13, 2001, both parts were streamlined under the name Vivendi Universal Games.

In 2002, Blizzard was able to reacquire rights for three of its earlier Silicon & Synapse titles, The Lost Vikings, Rock n' Roll Racing and Blackthorne, from Interplay Entertainment and re-release them for the Game Boy Advance handheld console.

In 2004, Blizzard opened European offices in the Paris suburb of Vélizy, Yvelines, France.

With the success of World of Warcraft, Blizzard Entertainment organized the first BlizzCon fan convention in October 2005 held at the Anaheim Convention Center. The inaugural event drew about 6,000 people and became an annual event which Blizzard uses to announce new games, expansions, and content for its properties.

On July 9, 2008, Activision merged with Vivendi Games, culminating in the inclusion of the Blizzard brand name in the title of the resulting new holding company, Activision Blizzard.

On October 3, 2018, Mike Morhaime announced his plans to step down as the company president and CEO while remaining an advisor to the company; he formally left on April 7, 2019. Morhaime was replaced by J. Allen Brack, the executive producer on World of Warcraft.

Frank Pearce announced he would be stepping down as Blizzard's Chief Development Officer on July 19, 2019, though will remain in an advisory role similar to Morhaime. Michael Chu, lead writer on many of Blizzard's franchises including Diablo, Warcraft, and Overwatch, announced he was leaving the company after 20 years in March 2020.

On January 22, 2021, Activision transferred Vicarious Visions over to Blizzard Entertainment, stating that the Vicarious Visions team had better opportunity for long-term support for Blizzard. Vicarious had been working with Blizzard for about two years prior to this announcement on the planned remaster of Diablo II, Diablo II: Resurrected, and according to Brack, it made sense to incorporate Vicarious into Blizzard for ongoing support of the game and for other Diablo games including Diablo IV. Vicarious was completely merged into Blizzard by April 12, 2022.

Blizzard acquired Proletariat, the developers of Spellbreak, in June 2022 as to help support World of Warcraft. The 100-employee studio remained in Boston but will shutter Spellbreak as they move onto Warcraft.

Activision Blizzard was the subject of a lawsuit from the California Department of Fair Employment and Housing in July 2021, asserting that for several years the management within Blizzard as well as Activision promoted a "frat boy" atmosphere that allowed and encouraged sexual misconduct towards female employees and discrimination in hiring practices. As a result of the California lawsuit and of delays and release issues with their more recent games, Activision Blizzard's stock faced severe pressure. Subsequently, Microsoft seized the opportunity to become one of the largest video game companies in the world and announced its intent to acquire Activision Blizzard and its subsidiaries, including Blizzard, for $68.7 billion in January 2022. This exchange marks the largest acquisition in tech history, surpassing the $67 billion Dell-EMC merger from 2016. The deal closed on October 13, 2023, and Activision Blizzard moved into the Microsoft Gaming division. While part of the larger Microsoft Gaming division, Blizzard Entertainment retains its function as the publisher of games developed by their studios.

On January 25, 2024, Blizzard President Mike Ybarra and Chief Design Officer Allen Adham announced they would be leaving the company. On January 29, 2024, Johanna Faries, the former general manager of the Call of Duty series, was named Blizzard Entertainment's new president, taking office on February 5.

Blizzard Entertainment hosts annual gaming conventions for fans to meet and to promote their games: the first BlizzCon was held in October 2005 at the Anaheim Convention Center in Anaheim, California, which is where all of their conventions have been held since. BlizzCon features game-related announcements, previews of upcoming Blizzard Entertainment games and content, Q&A sessions and panels, costume contests, and playable demos of various Blizzard games. Blizzard WorldWide Invitationals were events similar to BlizzCon held in South Korea and France between 2004 and 2008.