Apollo Geist is the chief of security of the Government of Darkness and the secondary antagonist of Kamen Rider X. He is the one in charge of assassinating rogue or traitorous members of the G.O.D. organization. He later reappears as a Dai-Shocker commander and the main antagonist of Kamen Rider Decade.

He was portrayed by Yasuhiko Uchida in Kamen Rider X. In Kamen Rider Decade and the film Let's Go Kamen Riders he was portrayed by Kazuhisa Kawahara. In Super Hero Taisen he was voiced by Kimito Totani. In Battride Wars he was voiced by Miyuki Sawashiro.

Apollo Geist is G.O.D.'s Chief of Security, armed with the Geist Cutter shield and the Apollo Shot shotgun, his human appearance wears a white tuxedo with black gloves until he invokes "Apollo Change". He has his own motorcycle branded with his Apollo Geist logo. His job is to execute any G.O.D member who considered useless. Destroyed himself using his Arm Bomb after he was defeated by X's X Finishing Kick when he tried to trick him by shaking hand.