Monolith Soft, Incorporated or MLSI (株式会社モノリスソフト) is a Japanese video game development company known for the development of the Baten Kaitos series alongside co-developer, Tri-Crescendo.

MLSI was founded in 1999 by producer Hirohide Sugiura after he left Square Co. and accepted investment from Namco. In May of 2007, Nintendo purchased controlling interest in the company from Namco Bandai making MLSI a first party developer under Nintendo. Since the aquisition, MLSI regularly develops for both Nintendo and Namco Bandai. Since handling production of most aspects besides programming, sound engineering and battle system design of the Baten Kaitos series under Baten Kaitos co-designer Yasuyuki Honne, MLSI has gone on to develop Dragon Ball Kai for the DS under Honne as well as various other titles under different leads, including Xenoblade for the Wii, of which Honne created concept art for.

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