| Robert J. Le Roy | |
| Birth Date: | 30 September 1943 |
| Birth Place: | Ottawa, Ontario, Canada |
| Death Place: | Waterloo, Ontario, Canada |
| Occupation: | Chemist |
| Known For: | LeRoy radius |
| Website: | Department of Chemistry, LeRoy |
Robert J. Le Roy (September 30, 1943 – August 10, 2018) was a Canadian chemist. He held the distinguished title of University Professor at the University of Waterloo.
His work on the Morse/Long-range potential with his former student Nike Dattani of Oxford University was referred to as a "landmark in diatomic spectral analysis".[1] In the landmark work, the C3 value for atomic lithium was determined to a higher-precision than any atom's previously measured oscillator strength, by an order of magnitude. This lithium oscillator strength is related to the radiative lifetime of atomic lithium and is used as a benchmark for atomic clocks and measurements of fundamental constants.[2]