Toaru Majutsu no Index (とある魔術の禁書目録（インデックス）, lit. A Certain Magical Index) is a Japanese light novel series written by Kazuma Kamachi (鎌池 和馬) and illustrated by Kiyotaka Haimura (灰村 キヨタカ). The series is published by ASCII Media Works under their Dengeki Bunko imprint. There are currently 53 published volumes of the novels, including 5 side story volumes. Regularly placing in the top 10 of the Kono Light Novel ga Sugoi! rankings, it was named the Best Novel Series of 10 Years in Kono Light Novel ga Sugoi! 2014. A sequel novel series titled Shinyaku Toaru Majutsu no Index (新約 とある魔術の禁書目録（インデックス）, lit. A Certain Magical Index: New Testament) began publishing in 2011 and concluded in July 2019 with its 23rd installment. A new sequel novel series titled Souyaku Toaru Majutsu no Index (創約 とある魔術の禁書目録（インデックス）, lit. A Certain Magical Index: Genesis Testament) began publishing in 2020.
The series has produced a manga with 24 published volumes, three anime seasons based on the contents of the original novels and inspired a PSP game. The anime adaptation has also inspired an animated film titled Gekijōban Toaru Majutsu no Index: Endymion no Kiseki (劇場版 とある魔術の禁書目録（インデックス） エンデュミオンの奇蹟, lit. A Certain Magical Index the Movie: Miracle of Endymion) which in turn inspired a PSP game tie-in and manga adaptation with 2 published volumes. Furthermore, the series has collaborated the Cyber Trooper Virtual-On series with a novel, a manga adaptation with 3 published volumes and a sequel PS4/Vita game.
The series has also produced a spin-off manga titled Toaru Kagaku no Railgun (とある科学の超電磁砲（レールガン）, lit. A Certain Scientific Railgun), which currently has 16 published volumes and has also been adapted into three anime seasons and inspired an OVA and a PSP game as well as its own spin-off: Astral Buddy, which has completed serialization with 4 published volumes. A second spin-off manga titled Toaru Kagaku no Accelerator (とある科学の一方通行(アクセラレータ), lit. A Certain Scientific Accelerator) has completed serialization with 12 published volumes and has recently been adapted into an anime.