Attack on Titan (Japanese: 進撃の巨人 Shingeki no Kyojin, lit. "Advancing Giants") is a Japanese manga series written and illustrated by Hajime Isayama. It is set in a world where humanity lives inside cities surrounded by enormous walls; a defense against the Titans, gigantic humanoids that eat humans seemingly without reason. The story initially centers on Eren Yeager, his adopted sister Mikasa Ackerman and childhood friend Armin Arlert, who joins the military to fight the Titans after their home town is invaded and Eren's mother is eaten. However, as the story progresses and the truths about the Titans are slowly revealed to the reader, the narrative shifts to encompass Historia Reiss, squad leader Levi, and other supporting characters.
A spin-off light novel series began in December 2011, and has received a manga adaptation. An additional light novel series and three additional spin-off manga series are also being serialized. Attack on Titan and three spin-off manga are published in North America by Kodansha Comics USA, while the novels are published by Vertical.
Attack on Titan has become a commercial success. As of July 2015, the manga has 52.5 million copies in print, with 50 million copies in Japan and 2.5 million copies overseas.