Kamen Rider × Kamen Rider Fourze & OOO: Movie War Mega Max (仮面ライダー×仮面ライダー フォーゼ&オーズ MOVIE大戦MEGA MAX, Kamen Raidā × Kamen Raidā Fōze Ando Ōzu Mūbī Taisen Mega Makkusu) is a 2011 film in the Kamen Rider series that was directed by Koichi Sakamoto. It features the casts of Kamen Rider Fourze and Kamen Rider OOO, and opened in Japanese theaters on December 10, 2011.

Movie War Mega Max is divided into five parts: Beginning: Fight! Legendary Seven Riders (幕開け 戦え! 伝説の七人ライダー, Makuake Tatakae! Densetsu no Shichinin Raidā), which focuses on the first seven Kamen Riders (One, Two, V3, Riderman, X, Amazon, and Stronger); Kamen Rider OOO: Ankh's Resurrection, the Medals of the Future, and the Leading Hope (仮面ライダーオーズ アンク復活と未来のメダルとつながる希望, Kamen Raidā Ōzu Anku Fukkatsu to Mirai no Medaru to Tsunagaru Kibou); Fuuto, the Conspiracy Advances: Gallant! Kamen Rider Joker (風都 暗躍する陰謀 颯爽! 仮面ライダージョーカー, Fūto Anyaku suru Inbō Sassō! Kamen Raidā Jōkā); Kamen Rider Fourze: Nadeshi-Ko De-Scend (仮面ライダーフォーゼ 撫・子・降・臨, Kamen Raidā Fōze Nadeshi Ko Kō Rin), in which the cast of Kamen Rider Fourze encounter and protect a strange girl that Gentaro Kisaragi falls in love with from the Horoscopes and Foundation X's Super Evolved Lifeform Mutamits (超進化生命ミュータミット, Chō Shinka Seimei Myūtamitto); and Movie War Mega Max: Gather! Warriors of Glory (MOVIE大戦MEGA MAX 集結せよ! 栄光の戦士たち, Mūbi Taisen Mega Makkusu Shūketsuseyo! Eikō no Senshi-tachi), where Foundation X's Lem Kannagi goes rogue to achieve world domination.