Eugen Grosche (11 March 1888, in Leipzig – 5 January 1964), also known as Gregor A. Gregorius, was a German occultist and author.
He was founder and Grandmaster of the lodge Fraternitas Saturni from 1926 till 1964.
The actual accomplishment of Gregorius and the FS was a more or less cohesive synthesis of Ancient and Accepted Scottish Rite Freemasonry, Luciferianism, astrological mythology, Crowleyanity (or Thelemism), sex-magical practices of the old O.T.O., various Indian yogic systems, and medieval and modern doctrines of alchemy and ritual magic.
After World War II Gregorius reformed Fraternitas Saturni.
In 1954 he published Die magische Erweckung der Chakra, and in 1960 the novel Exorial.