Foundation X is a recurring antagonist faction in the Neo-Heisei era of Kamen Rider. They are an underground research organization focusing on illegal projects with phenomenal energetic potentials. They make their debut in Kamen Rider W as the backers of Museum and later appear as the main antagonist faction in Kamen Rider x Kamen Rider Fourze & OOO: Movie War Mega Max and Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders, as well as the V-Cinema Kamen Rider W Returns: Kamen Rider Eternal.
The massive projects they focus would provide in return immeasurable profit and research data from sponsoring different organizations to their respective project. They first debut in Kamen Rider W, sponsoring the Musuem for their Gaia Memory research, involving the investigating the true Gaia Memory and the artificial Gaia Memories. After Ryubee Sonozaki dies, the foundation takes over the Gaia Impact project.
But after the death of Jun Kazu, Foundation X cancels all Gaia Memory research to focus on other prospective projects, such as the O Medals and later the Cosmic Energy research of Mitsuaki Gamou. Foundation X is also known for creating Dummy Kaijin, which are kaijin that resemble and hold the powers of the kaijin they represent, but are actually manifestations of Gaia Memories, Medals, or Cosmic Energy.
All members of Foundation X wear white business suits, classifying them as both researchers and business merchants of death.
- Neon Ulsland - Leader
- Jun Kazu - Researcher
- Tabata - Employee
- Doctor Prospect - Scientist
- Lloyd - Bodyguard
- Shion - Bodyguard
- Lem Kannagi - Scientist
- Katal - Subordinate
- Solaris - Subordinate
- Chancellor Kiima - Executive
- Female Executive Member of Foundation X
- Kaisei Mogami - Scientist/ Researcher
- Callas - Leader
- Canaria - Double Agent
- Sonozaki Family
- Badan Empire
- Genm Corp
- Machina Vision
- Namba Heavy Industries
- Blood Tribe
- Foundation X is the financial backer of many evil organizations and research facilities. Their manner of involvement with other organizations is somewhat similar to Shocker and the Great Leader's support of evil organizations in the Showa Era.
- Foundation X's name is similar to the Foundation from Shin Kamen Rider: Prologue, possibly suggesting a link between them. In fact, the book "General Facts of Kamen Rider" implies that they are connected.
- In the graphic novel adaptation of Cyborg 009, Foundation X is revealed to be a supporter of the death merchant organization Black Ghost and is mentioned several times as "The Foundation". Its name is revealed towards the end when one of its unseen operatives kills Sekar on an unnamed space station for his betrayal and failure to defeat the 00 Cyborgs.