Fortified Zone, known in Japan as Ikari no Yōsai (怒りの要塞, Ikari no Yōsai, "The Fortress of Fury") is a 1991 video game developed and published by Jaleco for the Game Boy. It was first released in Japan on February 26, 1991 and later released in North America in September 1991. It was later added to the 3DS Virtual Console on July 7, 2011, but the Australia region had it added on July 28, 2011.

Fortified Zone was ahead of its time in allowing the player to switch between characters during game play. Each character has their own strengths and weaknesses: Masato (the male mercenary) uses all the special weapons, but cannot jump. Mizuki (the female mercenary) can jump, but cannot use the special weapons. A top-down shoot-'em-up, the game had four multi-room levels, titled 'Field', 'Jungle', 'Caves' and 'Complex'. At the end of each level the player faces a 'boss' character: a cannon installation, a supertank, a dragon, a bulldozer and a large assault vehicle as the final boss. Items that can be picked up in gameplay include medical packs, flamethrowers, hand grenades, rocket launchers, 3-way machine guns and chain guns.