Kingdom Hearts (キングダムハーツ, Kingudamu Hātsu?) is a series of action role-playing games developed and published by Square Enix (formerly Square). It is the result of a collaboration between Square and Disney Interactive Studios and is under the direction of Tetsuya Nomura, a longtime Square character designer. Kingdom Hearts is a crossover of various Disney settings based in a universe made specifically for the series. In addition, it has an all-star voice cast which includes many of the Disney characters' official voice actors. Characters from Square Enix's Final Fantasy series make appearances and interact with the player and Disney characters. The series centers around the main character Sora's search for his friends and his encounters with Disney and Final Fantasy characters on their worlds.

The Kingdom Hearts series currently consists of four games across different video game platforms, and future titles are planned. Most of the games in the series have been both critically acclaimed and commercially successful, though each installment has seen varying levels of success. As of September 2008, the Kingdom Hearts series has shipped over 12.0 million copies worldwide, with 2.0 million copies in PAL regions, 3.0 million copies in Japan, and 5.6 million copies in North America. There have been several types of merchandise released along with the games, such as soundtracks, figurines, and companion books. In addition, the series has been adapted into a manga series and novels.

Source: Wikipedia