Oleg Ivanovich Zatsarinny (1953–2021) was a Ukrainian-American theoretical physicist noted for his contributions to all aspects of research related to electron scattering in atoms. He was awarded the status of Fellow in the American Physical Society, after he was nominated by his Division of Atomic, Molecular & Optical Physics in 2008, for "the development of the B-Spline R-matrix method with non-orthogonal orbital sets for atomic structure calculations of exceptional accuracy and benchmark calculations for excitation and ionization of complex atoms and ions by photon and electron impact."