Lisa Randall (born June 18, 1962) is an American theoretical physicist and leading expert on particle physics and cosmology. She is the Frank B. Baird, Jr. Professor of Science on the physics faculty of Harvard University. Her research includes elementary particles and fundamental forces and she has developed and studied a wide variety of models, the most recent involving extra dimensions of space. She has advanced the understanding and testing of the Standard Model, supersymmetry, possible solutions to the hierarchy problem concerning the relative weakness of gravity, cosmology of extra dimensions, baryogenesis, cosmological inflation, and dark matter. Her best-known contribution is the Randall–Sundrum model, first published in 1999 with Raman Sundrum.