Peter Malcolm Wallace Gill (born 9 November 1962)[1] is a New Zealand theoretical and computational chemist known for his contribution to density functional theory (DFT).

He is an early and main contributor to the computational chemistry software Q-Chem and was the president of the company during 1998–2013.

He is especially known for developing the PRISM algorithm for evaluating two-electron integrals and linear-scaling DFT, as well as self-consistent field method for excited state electronic structure.

During this time, he investigated hemi-bonding and the convergence of perturbation theory in quantum chemistry.

[3][4] After graduation, he conducted postdoctoral work with John Pople at Carnegie Mellon University from 1988 to 1993.