Johann Juncker (December 23, 1679 in Londorf, Hesse – October 25, 1759 in Halle) was a German physician and chemist.
Juncker was a leader in the Pietist reform movement as it applied to medicine.
He directed the Francke Foundations and initiated approaches to medical practice, charitable treatment, and education at the University of Halle that influenced others internationally.
He was a staunch proponent of Georg Ernst Stahl and helped to more clearly present Stahl's phlogiston theory of combustion.