The Familiar of Zero is a Japanese fantasy light novel series written by Noboru Yamaguchi, with illustrations by Eiji Usatsuka. Media Factory published 20 volumes between June 2004 and February 2011. The series was left unfinished due to the author's death in 2013, but was later concluded in two volumes released in February 2016 and February 2017 with a different author, making use of notes left behind by Yamaguchi.