Johann Daniel Mylius (c. 1583 – 1642) was a composer for the lute, and writer on alchemy. Born at Wetter in present-day Hesse, Germany, he went on to study theology and medicine at the University of Marburg. He was the brother-in-law and pupil of Johann Hartmann (1568–1613).^[1]

In 1616, while still a medical student, Mylius published Duncan Burnet's Iatrochymicus.^[2] The Opus medico-chymicum, Mylius' own alchemical work, was published two years later. He is known for the collection Thesaurus gratiarum (1622) of pieces for the lute.^[3] In the same year his Philosophia Reformata was published.^[4] Mylius was the personal physician of Moritz of Hessen and his patrons included Maurice and Frederick Henry of Nassau.