Grant Tremblay (born March 13, 1984) is an American astrophysicist notable for research on supermassive black holes, science communication, and public advocacy for large space telescopes.

His interest in astronomy and astrophysics was triggered by the 1994 Comet Shoemaker–Levy 9 impact of Jupiter, and by using a small telescope in his backyard while growing up in Maine.

His Doctoral advisors were Stefi Baum and Christopher O'Dea, and his Ph.D. Thesis was titled "Feedback Regulated Star Formation in Cool Core Clusters of Galaxies".

In 2016, Tremblay and collaborators published a paper in the journal Nature reporting Atacama Large Millimeter Array (ALMA) observations of cold molecular gas clouds falling toward a supermassive black hole in the brightest cluster galaxy of Abell 2597, a well known cool core cluster of galaxies.

He is the author of two books for the general public (Light from the Void: Twenty Years of Discovery with NASA's Chandra X-ray Observatory[7] and What do Black Holes Eat for Dinner?.