20th Century Boys is a Japanese manga series written and illustrated by Naoki Urasawa. It was originally serialized in Shogakukan's seinen manga magazine Big Comic Spirits from 1999 to 2006, with the 249 chapters published into 22 tankōbon volumes. A 16 chapter continuation, titled 21st Century Boys , ran in the same magazine from 2006 to 2007 and was gathered into two tankōbon volumes. It tells the story of Kenji Endo and his friends, who notice that a cult-leader known only as "Friend" is out to destroy the world, and that his cult icon bears a striking resemblance to a symbol developed during their childhoods. The series makes many references to a number of manga and anime from the 1960s–1970s, as well as to classic rock music, its title being taken from T. Rex's song "20th Century Boy".

Naoki Urasawa is a Japanese manga artist and musician. He has been drawing manga since he was four years old, and for most of his professional career has created two series simultaneously. The stories to many of these were co-written in collaboration with his former editor, Takashi Nagasaki. Urasawa has been called one of the artists that changed the history of manga and has won numerous awards, including the Shogakukan Manga Award three times, the Tezuka Osamu Cultural Prize twice, and the Kodansha Manga Award once. South Korean filmmaker Bong Joon-ho called him "the greatest storyteller of our time", while Dominican-American writer Junot Díaz proclaimed Urasawa to be a national treasure in Japan. By December 2021, his various works had over 140 million copies in circulation worldwide, making him one of the best-selling authors of all time.