Written by Hiroshi Seko

Attack on Titan: Lost Girls (進撃の巨人 LOST GIRLS Shingeki no Kyojin: Lost Girls?) is a Japanese novel written by Hiroshi Seko. The book is a spinoff of the manga series Attack on Titan by Hajime Isayama. A manga adaptation began serialization in August 2015 and ran until May 2016.

The novel is based off two mini-visual novels from Nitroplus which were included with the third and sixth volumes of the Attack on Titan anime Blu-ray release. The first, Lost in the Cruel World, was written by Seko and was released on September 18, 2013. The second, titled Wall Sina, Goodbye, also by Seko, was released on December 18, 2013.

The novel is written by Hiroshi Seko, who worked as a scriptwriter for the anime. Kodansha published it in December 2014 under their Kodansha Comics Deluxe imprint. It consists of three short stories, titled "Lost in the cruel world", "Wall Sina, Goodbye", and "Lost Girls".

North American publisher Vertical announced their license to the novel at Anime Expo 2015.