Hilaire Marin Rouelle (February 1718, Mathieu–April 7, 1779, Paris) is a French chemist.

Commonly cited as the 1773 discoverer of urea, he is not the first to do so.

Dutch scientist Herman Boerhaave had discovered this chemical as early as 1727.

Rouelle is known as "le cadet" (the younger) to distinguish him from his older brother, Guillaume-François Rouelle, who is also a chemist.