Donald Gene Truhlar (born 27 February 1944, Chicago) is an American scientist working in theoretical and computational chemistry and chemical physics with special emphases on quantum mechanics and chemical dynamics.

[4][5] Truhlar received a B.A., from St. Mary's College of Minnesota (1965), and a Ph.D., from Caltech (1970), under Aron Kuppermann.

Truhlar is known for his contributions[7] to theoretical chemical dynamics of chemical reactions; quantum mechanical scattering theory of chemical reactions and molecular energy transfer; electron scattering; theoretical kinetics and chemical dynamics; potential energy surfaces and molecular interactions; path integrals; variational transition state theory; the use of electronic structure theory for calculations of chemical structure, reaction rates, electronically nonadiabatic processes, and solvation effects; photochemistry; combustion chemistry; heterogeneous, homogeneous, and enzyme catalysis; atmospheric and environmental chemistry; drug design; nanoparticle structure and energetics; basis set development; and density functional theory, including the Minnesota Functionals.

He was a visiting fellow at the Battelle Memorial Institute (1973) and at the Joint Institute for Laboratory Astrophysics (1975–76), and was named an Alfred P. Sloan Foundation Research Fellow (1973).

He received the NSF Creativity Award (1993), the ACS Award for Computers in Chemical and Pharmaceutical Research (2000), the Minnesota Award (2003) ("for outstanding contributions to the chemical sciences"), the National Academy of Sciences Award for Scientific Reviewing (2004); the ACS Peter Debye Award for Physical Chemistry (2006), the Lise Meitner Lectureship Award (2006), the Schrödinger Medal of The World Association of Theoretical and Computational Chemists (2006), the Dudley R. Herschbach Award for Research in Molecular Collision Dynamics (2009), Doctor honoris causa of Technical University of Lodz, Poland, (2010), the Royal Society of Chemistry Chemical Dynamics Award (2012), the APS Earle K. Plyler Prize for Molecular Spectroscopy and Dynamics (2015), the 2019 ACS Award in Theoretical Chemistry (2018),[10] and the 2023 Joseph O. Hirschfelder Prize in Theoretical Chemistry.