Willis Harmon Ray (born April 4, 1940) is an American chemical engineer, control theorist, applied mathematician, and a Vilas Research emeritus professor at the University of Wisconsin–Madison[1] notable for being the 2000 winner of the prestigious Richard E. Bellman Control Heritage Award and the 2019 winner of the Neal Amundson Award.

Harmon earned his bachelor's degree in chemical engineering in 1963 from Rice University; and his PhD in chemical engineering in 1966 from the University of Minnesota, under supervision of Professor Rutherford Aris.

[1] Harmon served as faculty member at the department of chemical engineering at the University of Waterloo (1966–1970), State University of New York at Buffalo (1970–1976), and the University of Wisconsin–Madison (after 1976).

He retired and became an emeritus faculty member at the University of Wisconsin in 2003.

During his tenure as a faculty member, Harmon supervised 53 PhD and 30 master's students.