Johann Georg Macasius (1617–1653) was a German physician. He was born in Eger, Bohemia (part of the Holy Roman Empire, now in the Czech Republic).
He received the Medicinae Doctorate from the University of Jena in 1638 under Johannes Musaeus with a thesis entitled De natura et causis externis. In 1640, he received a second Medicinae Doctorate from the University of Jena under Balthasar Widmarcter with a thesis entitled Disputatio de inflammatione.