Ronald James Gillespie, CM FRSC FRS[1] (August 21, 1924 – February 26, 2021)[2] was a British chemist specializing in the field of molecular geometry, who arrived in Canada after accepting an offer that included his own laboratory with new equipment, which post-World War II Britain could not provide.

He was responsible for establishing inorganic chemistry education in Canada.

[3] Gillespie did extensive work on expanding the idea of the Valence Shell Electron Pair Repulsion (VSEPR) model of Molecular Geometry, which he developed with Ronald Nyholm (and thus is also known as the Gillespie-Nyholm theory), and setting the rules for assigning numbers.

Gillespie has also done extensive work on interpreting the covalent radius of fluorine.

Gillespie's work on the bond length of fluorine focuses on theoretically determining the covalent radius of fluorine by examining its covalent radius when it is attached to several different atoms.