In demonology Phenex is a Great Marquis of Hell and has twenty legions of demons under his command. He teaches all wonderful sciences, is an excellent poet, and is very obedient to the conjuror.Although the All Powerful, Almighty, King of kings, Lord of lords, God, won't allow it, Phenex has hopes to return to heaven amongst the other non-fallen angels in one thousand and two hundred years more.

He is depicted as a phoenix, which sings sweet notes with the voice of a child, but the conjurer must warn his companions (for he has not to be alone) not to hear them and ask him to put in human shape, what he does after a while.

The etymology of his name is obviously the name of the mythical phoenix.

Other spellings: Pheynix, Phoenix.

See also The Lesser Key of Solomon, Ars Goetia.