King.com Limited is a Swedish video game developer and publisher that specialises in social games. Since 2016, it is one of 3 publishing businesses of Activision Blizzard. Headquartered in Stockholm and London, and incorporated in St. Julian's, Malta, King rose to prominence after releasing the cross-platform title Candy Crush Saga in 2012. It is considered as one of the most financially successful games utilising the freemium model. King was acquired by Activision Blizzard in February 2016 for US$5.9 billion, and operates as its own entity within that company. King is led by Todd Green, who holds the position of President. Gerhard Florin took over Melvyn Morris's role as chairman in November 2014. As of 2017, King employs 2,000 people.

In October 2023, Microsoft acquired parent company Activision Blizzard, maintaining that the company will continue to operate as a separate business. While part of the larger Xbox division, King retains its function as the publisher of games developed internally.

Prior to founding King, Riccardo Zacconi and Toby Rowland, the latter of whom is the only son of British businessman Tiny Rowland, had worked together on uDate.com, a dating website created by Melvyn Morris which, by 2003, was the second-largest such site in the world. Morris opted to sell the site to the leading dating website Match.com (a subsidiary of IAC) for $150 million in 2003. Zacconi and Rowland joined with Thomas Hartwig, Sebastian Knutsson, Lars Markgren and Patrik Stymne, all of whom had worked previously with Zacconi at the failed dot-com web portal Spray, to create a new company with angel investment provided by Morris, who became the company's chairman. The company was initially based out of Stockholm, Sweden, and started with the development of browser-based video games. The site, Midasplayer.com, was then launched in August of that year.

Initially, Midasplayer.com was not profitable, and nearly went bankrupt until a cash infusion from Morris on Christmas Eve of 2003 helped to finance the company. By 2005, the company had been able to turn a profit. During this year, the company raised $43 million by selling a large stake to Apax Partners and Index Ventures. This investment was the last one that the company received before its initial public offering in 2014. Midasplayer.com was rebranded King.com in November 2005. King.com continued to develop games for its web portal, which it would also share to other web portals like Yahoo! Overall, King had developed about 200 games for its portal. By 2009, the company was making about $60 million annually. Rowland departed the company in 2008 to found Mangahigh, a web portal aimed for educational math games, and sold his stake back to the company for $3 million in 2011. Angel investor and former board member Klaus Hommels sold his similar stake at the same time.

Around 2009, social network games on Facebook began to gain popularity, led primarily through games developed by Zynga. King.com saw a significant drop in players on their portal games as a result, and started to develop their own Facebook-based games using the games already developed on the King.com portal, with their first such game released in 2010. King.com used their web portal as a testing ground for new game ideas and determine which ones to bring to Facebook, as well as determining how to implement various microtransactions for tournament-style play into the Facebook games. Their first cross-platform web portal/Facebook game, Miner Speed, which allowed sharing of player information between platforms, was released in 2011, and was a simple match-3 tile game inspired by Bejeweled.

Following this model, in October 2011, the company released Bubble Witch Saga to both platforms. Bubble Witch Saga introduced the nature of a "saga" game: instead of playing the same gameboard for as long as the player could continue to match matches, the game offered individual levels that would challenge the player to complete certain goals in a limited number of turns. These saga elements allowed for the basics of social gameplay, but did not require the time investment that then-popular titles like Zynga's Farmville required; players could play just for a few minutes each day through the saga model. The formula proved extremely successful, and January 2012, Bubble Witch Saga had over 10 million players and was one of the most-played Facebook games. By April 2012, King.com had the second largest player count, around 30 million unique users, second only to Zynga on the Facebook platform. Facebook's director of games partnerships Sean Ryan described King.com's growth on the platform as "They were not a flash in the pan – they've been around seven years. But they came out of no where in an area that was unexpected." King.com next released Candy Crush Saga in April 2012, based on the popularity of its Candy Crush web-portal game and following the saga model from Bubble Witch Saga. The game attracted more than 4 million players within a few weeks.

The popularity of Bubble Witch Saga and Candy Crush Saga led King.com to start a new strategy into developing for the growing mobile game market, in a manner that would allow players to synchronise with the Facebook platform. Zacconi said that "As consumers and the industry focus more on games for mobile devices, launching a truly cross-platform Facebook game has been a top priority for King.com." A mobile version for iOS device of Bubble Witch Saga was released in July 2012, while the iOS mobile version of Candy Crush Saga was released in October 2012. Both games saw boosts in the number of unique players with the mobile introduction; King.com saw that previously declining player counts for Bubble Witch Saga become steady with the mobile version's release, while Candy Crush Saga saw more than 5.2 million unique players on Facebook in November 2012 and which were continuing to climb. Additionally, in-game advertising, which factored into about 15% of King.com's revenues, had increased ten-fold from 2011 into 2012. Users jumped to 408 million by the end of 2013. Revenues for King.com increased from a little over $62 million in 2011 to $1.88 billion in 2013.

In March 2013, on the ten-year anniversary of its founding, the company announced it was dropping the ".com" part of its branding and would continue on as just "King". In November 2014, King sued Korean company Avocado Entertainment for copying its Farm Hero Saga game in distributed game Forest Mania.