Akagi: Yami ni Oritatta Tensai (アカギ 〜闇に降り立った天才〜; lit. "Akagi: The Genius Who Descended into Darkness") is a Japanese manga series written and illustrated by Nobuyuki Fukumoto. First published in 1991 in Takeshobo's weekly magazine Kindai Mahjong, it is a spin-off prequel to the author's previous work Ten. It revolves around Shigeru Akagi, a boy who defeats yakuza members well versed in mahjong at 13. He returns to the game six years later, carrying a mythical status and still impresses his opponents.

It was adapted as two V-Cinema live-action films directed by Kenzō Maihara in 1995 and 1997. A 26-episode anime television series directed by Yūzō Satō was broadcast on Nippon Television from October 2005 to March 2006. Two live-action television dramas directed by Mitsuru Kubota aired on BS SKY PerfecTV! between July 2015 and June 2018. The series has also spawned several companion books, spin-off manga, video games, and other merchandise.

By February 2017, the Akagi manga series had over 12 million copies in circulation.