In demonology Marchosias is powerful Great Marquis of Hell, commanding thirty legions of demons. He is a strong and excellent fighter and very reliable to the conjurer, giving true answers to all questions. Marchosias hoped after one thousand and two hundred years to return to heaven with the non-fallen angels, but he is deceived in that hope.

He is depicted as a wolf, a she-wolf, or an ox, that under request changes shape into a man.

The name Marchosias comes from Late Latin 'marchio', marquis.

Other spellings: Marchocias.

See also The Lesser Key of Solomon, Ars Goetia.