A Certain Magical Index is a Japanese light novel series written by Kazuma Kamachi and illustrated by Kiyotaka Haimura, which has been published by ASCII Media Works under their Dengeki Bunko imprint since April 2004 in a total of three separate series. The first ran from April 2004 to October 2010, the second from March 2011 to July 2019, and the third from February 2020 to present.

A light novel is a type of popular literature novel native to Japan, usually classified as young adult fiction targeting teens to twenties. The definition is very vague, and wide-ranging.