Schwarz Stein is a Japanese visual kei electronic music duo formed by Hora (洞) and Kaya (迦夜) in 2001 (as "Rudolf Steiner"), who disbanded in 2004 and rebanded in 2014.

During its first three years of activity, the group consisted of Kaya on vocals (ex-Isola) and Hora (ex-Velvet Eden) as keyboardist and programmer.

The two originally worked together under the alias Rudolf Steiner until their signing to ex-Malice Mizer guitarist Mana's record label Midi:Nette.

The band was briefly reunited for the "Dis Inferno III: Last Year Party" event on December 15, 2004, hosted by their former label Midi:Nette.

In April 2011, both members announced on their respective web sites that Schwarz Stein would reunite for a single show on July 31 at Takadanobaba Area, to celebrate their 10th anniversary of working together.