Toshokan Sensō (図書館戦争, Toshokan Sensō? lit. Library War) is a Japanese light novel series by Hiro Arikawa, with illustrations by Sukumo Adabana. There are four novels in the series, though only the first novel is called Toshokan Sensō; the subsequent novels are named Toshokan Nairan, Toshokan Kiki, and Toshokan Kakumei. The novels were published by MediaWorks between February 2006 and November 2007. Two volumes of a spin-off series entitled Bessatsu Toshokan Sensō (別冊 図書館戦争, Bessatsu Toshokan Sensō? lit. Supplement: Library War) have also been published by ASCII Media Works. As of April 2008, the original four novels and volume one of the spin-off series have sold over 1.25 million copies in Japan. The story was inspired from the Statement on Intellectual Freedom in Libraries of the Japan Library Association.
A manga adaptation by Kiiro Yumi started serialization in the shōjo manga magazine LaLa on September 24, 2007 published by Hakusensha; another manga adaptation by Yayoi Furudori started serialization in the shōnen manga magazine Dengeki Daioh on November 21, 2007 published by ASCII Media Works. A twelve-episode anime adaptation by Production I.G began airing on Fuji TV's Noitamina programming block on April 11, 2008. Two Internet radio shows started in April 2008 meant to promote the series which are hosted by voice actors of the anime.