Kamen Rider OOO (仮面ライダーオーズ／ＯＯＯ, Kamen Raidā Ōzu?) is the twelfth series in the Heisei period run of the Kamen Rider Series, and the twenty-first overall. It began airing on September 5, 2010, the week following the conclusion of Kamen Rider Double, joining Tensou Sentai Goseiger in the Super Hero Time lineup. The series' titular Kamen Rider made a cameo appearance in the film Kamen Rider Double Forever: A to Z/The Gaia Memories of Fate. The catchphrase for the series is "I'm transforming!!!" (俺が変身する!!!, Ore ga henshin suru!!?).

Production

OOO will be written by Yasuko Kobayashi, known for the screenplays of Kamen Rider Ryuki, Den-O, and several Super Sentai Series. The creature designers are Yutaka Izubuchi, known for his work on the Lords in Kamen Rider Agito, and Tamotsu Shinohara, known for his work on the Mirror Monsters of Ryuki and the Orphnoch of Kamen Rider 555. Unlike several previous Heisei Rider Series, no alternate name has been given yet for the three O's in the title (Ｗ（ダブル） read as "Double" and 555（ファイズ） read as "Φ's/Phi's/Faiz") aside from an alternate spelling of the name of the main Kamen Rider: Ooz. Both "OOO" and "Ooz" are intended to be read as "O's", referring to the multiple uses of the letter O in the title as well as "multiple kings" (王ｓ, Ōzu). The title OOO signifies the three medals that the main Kamen Rider uses to transform as well as being representative of the infinity symbol () with an additional circle.

1. Medals, Underwear, and a Mysterious Arm (メダルとパンツと謎の腕, Medaru to Pantsu to Nazo no Ude)
2. Desire, Ice Pops, and Presents (欲望とアイスとプレゼント, Yokubō to Aisu to Purezento)
3. A Cat, Evolution, and a Glutton (ネコと進化と食いしん坊, Neko to Shinka to Kuishinbō)
4. Doubt, a Picture Message, and a Helping Hand (疑いと写メと救いの手, Utagai to Shame to Sukui no Te)
5. A Game of Tag, a Den, and a Celebrity (追いかけっこと巣とセレブ, Oikakekko to Su to Serebu)