|This article is about a/an organization in Kamen Rider W.|
Foundation X (財団Ｘ, Zaidan Ekkusu) is an underground research organization focusing on illegal projects with pheonominal energic potentials. 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 Gamo.
All members of Foundation X wear white business suits, classifying them as both researchers and business merchants of death. (死の商人)
- Main article: Jun Kazu
Jun Kazu (加頭 順, Kazu Jun) is a valuable Foundation X member who is a Quark/Necro-Over hybrid, and the Utopia Dopant, the final antagonist of Kamen Rider W.
- Main article: Tabata
Tabata (田端) is a researcher from Foundation X who picks up the T2 Gaia Memories from Kazu to take to the Foundation's headquarters in episode 44 of Kamen Rider W. However, as revealed in the opening of Kamen Rider W Forever: A to Z/The Gaia Memories of Fate, he is attacked en route in a helicopter to Foundation X's headquarters by Daido Katsumi who takes the T2 Eternal Memory as he escapes death when Tabata activated the suitcase's self destruct, killing himself as the helicopter explodes and the other T2 Gaia Memories spread throughout Futo.
- Main article: Neon Ulsland
Neon Ulsland (ネオン・ウルスランド, Neon Urusurando) is the woman in charge of Foundation X, usually researching Foundation X reports about unusual events or artifacts, such as NEVER or the O Medals, which are graded from A, B, C, D, or F. She is often seen with a stopwatch, as she is very strict when it comes to keeping schedules. She is shown to check her stopwatch frequently and doing strict allocations of time for matters, even interrupting others' talking and not sparing even a second more, should it affect her schedule. After Jun Kazu's defeat, she officially decides to end the foundation's Gaia Memory research.
- Main article: Doctor Prospect
Doctor Prospect (ドクター・プロスペクト, Dokutā Purosupekuto) was a Foundation X scientist studying the use of psychic ability and created an army of psychic-powered soldiers known as Quarks (クオークス, Kuōkusu). He can transform into the Eyes Dopant (アイズ・ドーパント, Aizu Dōpanto) and is the main antagonist in Kamen Rider W Returns: Kamen Rider Eternal.
Lloyd (ロイド, Roido) was one of Doctor Prospect's Quarks bodyguards before he was killed off by Gozo Domoto.
Shion (シオン) was one of Doctor Prospect's Quarks bodyguards before she was killed off by Kyosui Izumi.
- Main article: Lem Kannagi
Lem Kannagi (レム・カンナギ, Remu Kannagi) was a Foundation X researcher who, before the events of Kamen Rider x Kamen Rider Fourze & OOO Movie War Megamax, he was known throughout Foundation X for successfully creating the Super Evolved Lifeform Mutamids. He then was granted funding for researching the time anomaly and SOLU that crashed to earth, and created the GingaOh driver using Kamen Rider Poseidon's Core Medals, and the SOLU Switch created from the SOLU that had become Nadeshiko Misaki. However, he betrayed his supervisor and all of Foundation X, and revealed his intention to use the GingaOh Driver rule not only the Earth, but the entire galaxy as the Super Galaxy King (超銀河王, Chō Ginga Ō). He was destroyed, as the Super Galaxy King by the combination of OOO's Super TaToBa Kick and Fourze's Double Rocket Drill Kick