The Saga of Tanya the Evil, known in Japan as Yōjo Senki (幼女戦記), is a Japanese light novel series written by Carlo Zen and illustrated by Shinobu Shinotsuki. It began serialization online in 2010, on the user-generated novel publishing website Arcadia. Enterbrain acquired the series in October 2013 and has published fourteen volumes by September 2023. A manga adaptation with art by Chika Tōjō began serialization in Kadokawa Shoten's Comp Ace magazine from April 2016.
The series focuses on a salaryman whose reincarnation as the titular character living in an alternate version of World War I leaves her to be trapped in an endless cycle of reincarnation. Willing to avoid being killed whilst dying of natural causes, Tanya must take it upon herself to don a bloodthirsty, sadist ego in hopes of joining the ranks of the Empire's Mage Corps as part of her plan to become a seemingly indestructible foe.
An anime television series adaptation by NUT was broadcast on Japanese television from January to March 2017. Saga of Tanya the Evil: The Movie, a theatrical film taking place after the events of the anime series, was released in Japan in February 2019. A second season is set to premiere in July 2026.