X

, also known as X/1999, is a shōjo manga series created by Clamp, a creative team made up by Satsuki Igarashi, Nanase Ohkawa, Tsubaki Nekoi, and Mokona. It premiered in Monthly Asuka's May 1992 issue and ran there until the magazine's editors showed concern in the increasingly violent stories.

Kadokawa Shoten collected and published the individual chapters in 18 tankōbon volumes, with five chapters published in the book "All about Clamp". All but several final chapters have been published. It has been adapted into a series of audio dramas, a 1996 animated feature film and a television series in 2001 with the two latter produced by Madhouse. Viz Media published all 18 volumes in North America, while the film and the TV series have released in DVDs by Manga Entertainment and Geneon, respectively.

Plot
His destiny has finally arrived as the young Shirou Kamui returns to Tokyo after 6 years. A powerful psychic, Kamui vows to protect the happiness of his childhood friends Fuuma and Kotori, even if it means avoiding them. But fate is cruel, whether or not Kamui wants to be involved; he holds the future of the world in his hands, given the choice of becoming a Dragon of Heaven or a Dragon of Earth. The Seven Seals gather, and so do the Seven Angels; all individuals who have their destiny carved out as one who would battle for the fate of the world. What future will Kamui choose to become reality?