Touhou Project (東方Project) is a series of bullet hell games created independently by the developer ZUN (Jun'ya Ota). There are 19 mainline games, 13 spin-off games, as well as print works, music albums, and a large body of unofficial fan-content. The mainline Touhou games are generally split into two eras: PC-98 and Windows. The PC-98 games were released from 1997-98; although these installments are quite dissimilar from the Windows games, they laid down the framework for the rest of the series and introduced many important characters. After a long break, the Windows era of Touhou began in 2002 with the game Embodiment of Scarlet Devil. Touhou games continued to be released today, with the latest installment - Unfinished Dream of All Living Ghost (Touhou 19) - being released in August of 2023 at Comiket.

One interesting and unique thing about Touhou is the amount of derivative works it has inspired. Even if you don't know anything about Touhou, there's a very large chance you've come across Touhou fan content; some of the most popular works include Bad Apple, Marisa Stole the Precious Thing, Overdrive, and many more. One of the main reasons why Touhou has such a large amount of fan content is due to ZUN encouraging fans and artists to use the content of the games creatively. ZUN himself has even collaborated with doujin music and game creators to create fan content, encouraging more and more people to put their spin on the games.

Background by 青葉 HAL, sprites from Touhou 7.5