Takashi Nagasaki (長崎尚志, born January 14, 1956) is a Japanese author, manga writer and former editor of manga. He started his professional career at Shogakukan in 1980 and worked as an editor on the publisher's various manga magazines, including as editor-in-chief of Big Comic Spirits from July 1999 to 2001. Since becoming freelance, Nagasaki has worked as an author under various pen names, such as Keishi Edogawa (江戸川啓視), Garaku Toshusai (東周斎雅楽), Big O (ビッグ・オー) and Richard Woo (リチャード・ウー).

He is best known for his collaborations with Naoki Urasawa, such as Pluto (2003–2009) and Billy Bat (2008–2016). The Kobe Shimbun wrote that Nagasaki brought the concept of a producer into the manga industry, and in doing so "established a new relationship with manga artists." Brian Ruh of Anime News Network described Nagasaki as the only editor who "has risen to the level of co-creator alongside the artist."