Marcel Gilles Jozef Minnaert (February 12 1893 – October 26 1970) was a Belgian astronomer.

He specialized in spectroscopy and the study of stellar atmospheres.

He won the Gold Medal of the Royal Astronomical Society in 1947 and the Bruce Medal in 1951.

In 1998 the University of Utrecht named a 9200 m² building after him, the Minnaert Building

In 2003 dr Leo Molenaar wrote a 600 page biography on Marcel Minnaert. See his site for a short biography.