Twenty-First Century Fox, Inc., which did business as 21st Century Fox, was an American multinational mass media and entertainment conglomerate based in Midtown Manhattan, New York City. It was formed on June 28, 2013, as the legal successor to News Corporation, while the second News Corporation was formed the same day as a spin-off. 21st Century Fox was the legal successor to News Corporation dealing primarily in the film and television industries. It was the United States' fourth-largest media conglomerate by revenue, up until its acquisition by the Walt Disney Company in 2019. The second News Corporation, which is doing business as News Corp, was spun off from the first News Corporation and holds Rupert Murdoch's print interests and other media assets in Australia (both owned by him and his family via a family trust with 39% interest in each). Murdoch was co-executive chairman, while his sons Lachlan Murdoch and James Murdoch were co-executive chairman and CEO, respectively.

21st Century Fox's assets included the Fox Entertainment Group—owners of the 20th Century Fox film studio (the company's partial namesake), the Fox television network, and a 73% stake in National Geographic Partners—the commercial media arm of the National Geographic Society, among other assets. It also had significant foreign operations, including the prominent Indian television channel operator Star India. The company ranked No. 109 in the 2018 Fortune 500 list of the largest United States corporations by total revenue.

On December 14, 2017, The Walt Disney Company agreed to acquire 21st Century Fox for $52.4 billion in stock. After Comcast mounted an all-cash bid of $65 billion, Disney increased its offer to $71.3 billion in cash and stock. Comcast dropped its bid on July 19, 2018, to instead acquire Sky plc, a British media group in which 21CF held a 39% stake. On July 27, 2018, Disney's offer was approved by shareholders of both companies. The sale covered the majority of 21CF's entertainment assets, including 20th Century Fox, FX Networks, and National Geographic Partners among others; while the sale also included 21CF's regional Fox Sports Networks, Disney was required to sell them within 90 days of the closure of the acquisition to comply with antitrust rulings. The remaining assets, consisting primarily of the Fox and MyNetworkTV networks, and 21CF's local station, news and national sports assets, were spun out into a new company named Fox Corporation, which began trading on March 19, 2019. Disney's acquisition of 21st Century Fox closed on March 20 of the same year.

21st Century Fox was formed by the splitting of entertainment and media properties from News Corporation. In February 2012, Natalie Ravitz accepted a position to become Rupert Murdoch's Chief of Staff at News Corporation.

News Corporation's board approved the split on May 24, 2013, while shareholders approved the split on June 11, 2013; the company completed the split on June 28 and formally started trading on NASDAQ on July 1.

Plans for the split were originally announced on June 28, 2012, while additional details and the working name of the new company were unveiled on December 3, 2012.

Murdoch stated that performing this split would "unlock the true value of both companies and their distinct assets, enabling investors to benefit from the separate strategic opportunities resulting from more focused management of each division." The move also came in the wake of a series of scandals that had damaged the reputation of the company's publishing operations in the United Kingdom. The split was structured so that the old News Corporation would change its name to 21st Century Fox and spin-off its publishing assets into a "new" News Corporation.

While the company was originally announced as the Fox Group, on April 16, 2013, Murdoch announced the new name as a way to leverage the already established 20th Century Fox brand name. Its logo was officially unveiled on May 9, 2013, featuring a modernized version of the iconic Fox searchlights designed by Pentagram.