Kingdom Hearts IV is an upcoming action role-playing game developed and published by Square Enix. It will be the fifteenth installment in the Kingdom Hearts series, beginning the "Lost Master" story arc. Set after the events of Kingdom Hearts III and Kingdom Hearts: Melody of Memory, returning protagonist Sora has become trapped in the life-like world of Quadratum, while his companions Donald Duck and Goofy try to find and rescue him.

Development on the next mainline entry after Kingdom Hearts III had begun by January 2020, with Kingdom Hearts IV formally announced in April 2022. Additional details for the game were revealed in mid-2026, along with the game's release window.

Kingdom Hearts IV is scheduled to be released on the Nintendo Switch 2, PlayStation 5, Windows, and Xbox Series X/S in late 2027.

Sora faces Heartless in the game. Parkour elements and Keyblade transformations return, with the Keyblade also able to transform into a grappling hook to traverse large distances. The game will have reaction commands similar to Kingdom Hearts II, and introduces a new "scrap and build" mechanic. More of Sora's "daily life" and his "day-to-day routines" are also explored. Mickey Mouse is also be a playable character, performing puzzle-based gameplay within paper-like levels set within a book. Donald Duck and Goofy are also playable, a first for the series. Team "limit" attacks also return.

Kingdom Hearts IV serves as the beginning of the "Lost Master" story arc. One of the worlds in which the game takes place is Quadratum, an expansive city set in a realistic world inspired by Tokyo, featuring a fictionalized Shibuya and Minami-Aoyama. Sora's apartment in Minami-Aoyama serves as the player's home base in the early part of the game. Quadratum serves as a hub world, with players returning there after traveling to other worlds. The original world Scala ad Calum returns.

Several worlds based on Disney properties also appear. Returning ones include the Hercules-based Underworld, while new ones include a world based on the 2017 Pixar film Coco.

Sora, a teenager who uses a key-shaped weapon called the Keyblade to battle the forces of darkness, reprises his role from previous games as the main protagonist and playable character of the game. Donald Duck and Goofy, the royal magician and knight captain of Disney Castle respectively, also return after having served as Sora's party companions. The game also features Strelitzia and Sigurd, Keyblade wielders who previously appeared in the mobile game Kingdom Hearts Union χ, along with Vali. Other main characters of the series, such as the protagonists of the games Kingdom Hearts Birth by Sleep and Kingdom Hearts 358/2 Days, will have minor roles in Kingdom Hearts IV, with Nomura open to finding a "good balance" with regards to including Final Fantasy characters that have been a part of the series. Mickey Mouse also returns from previous games. Disney and Pixar characters, who serve as members of Sora's party include Miguel and Héctor. Other Disney and Pixar character that appear, include Ernesto de la Cruz, and the villains Hades and Maleficent, the latter who plays a "very important role" in the game.

Though Kingdom Hearts III is the end of the "Dark Seeker Saga" which revolved around Xehanort, it had been decided where certain characters end up to potentially continue their stories in future games. The ending of Kingdom Hearts III and its downloadable content (DLC) Re Mind sees Sora's arrival in the city of Quadratum and the appearance of the character Yozora, who is the main character of the in-universe video game Verum Rex. Quadratum has design elements that evoke Shibuya from Square Enix's franchise The World Ends with You, as well as Final Fantasy Versus XIII, which was reworked to become Final Fantasy XV; Yozora's design is also similar to Noctis Lucis Caelum, the main protagonist of Final Fantasy XV, and part of his appearance mimics an early trailer for Versus XIII. Commentators believed series director Tetsuya Nomura, who was also the director of Versus XIII before it was reworked, was planning to implement some of his ideas from that game in a future Kingdom Hearts title. In March 2020, Nomura said Versus XIII and Verum Rex were "completely different" but an "unexpected development" between the two was occurring, and later confirmed the Shibuya in Quadratum was unrelated to that in The World Ends with You.