Knightmare, known in Japan as Majou Densetsu (魔城伝説 , Demon Castle Legend?), is a 1986 MSX vertical scrolling shooter computer game. The player is a knight, Popolon, who has to fight his way through several levels to defeat Hudnos and rescue Aphrodite.

Knightmare was an innovative upward-scrolling shoot 'em up game on the MSX system released as game cartridge. The top-view graphics were considered very sophisticated for its time, similar to other MSX games such as Nemesis and Penguin Adventure.

Konami also released a slightly altered version that could be bought from LINKS network. (Japanese "internet replacement" of the 80's) In this version you could submit high scores to online server.

It was brought without a license to the SG-1000 in Taiwan.