The Familiar of Zero (Japanese: ゼロの使い魔, Hepburn: Zero no Tsukaima) is a fantasy and comedy-oriented series of Japanese light novels 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 on April 4, 2013, but the series was concluded with a different author, making use of notes left behind by the late original author. The story features several characters from the second year class of a magic academy in a fictional magical world with the main characters being the inept mage Louise and her familiar from Earth, Saito Hiraga.
Between 2006 and 2012, the series was adapted by J.C.Staff into four anime television series and an additional original video animation episode. The first anime series was licensed by Geneon Entertainment in English, but the license expired in 2011. Sentai Filmworks has since re-licensed and re-released the first series and released the other three series in North America. A manga version drawn by Nana Mochizuki was serialized in Media Factory's manga magazine Monthly Comic Alive between August 2006 and October 2009. The manga was released by Seven Seas Entertainment in North America. Three additional spin-off manga were also created, as were three visual novels.