Yousei Teikoku, also known as Das Feenreich, is a gothic metal band from Nagoya, Aichi Prefecture, Japan. The band began as a collaboration between singer-songwriter Yui Itsuki and multi-instrumentalist/producer Takaha Tachibana. After several independent releases, the band signed with Lantis prior to its first major album in 2007.

The band has a mythological lore, in which the Fairy Empire, led by "Dictator for Life" (終身独裁官) YUI, tries to remind the human world of the existence of fairies. They do so through the establishment of "Fairy Empire 1st Military Band" (妖精帝國第参軍楽隊), which is represented by "ranks" that are given to the band's human members.

Vocals: Yui, "Dictator for Life"
Bass: Nanami, "Warrant Officer"
Drums: Gight, "Sergeant"
Guitar: XiVa & ryöga, "Corporal"

"Captain" Takaha Tachibana continues to produce and compose for the band despite retiring from live performance in 2019. Relu was the band's drummer from 2010-2013. Finally, Shiren was the band's lead guitarist from 2013-2018.