Matthew Benjamin Kleban is an American theoretical physicist who works on string theory and theoretical cosmology. He is the chair of the Department of Physics and a professor at New York University, former director of the Center for Cosmology and Particle Physics, and a former member of the Institute for Advanced Study. His contributions to physics include:

• The discovery of the first distinct signature of the black hole singularity in AdS/CFT (with Lukasz Fidkowski, Veronika Hubeny and Stephen Shenker)
• Pioneering work on the subtleties of very late-time cosmology in the presence of a positive cosmological constant, and the "Boltzmann brain" problem (with Lisa Dyson and Leonard Susskind)
• A determination of the effects of cosmic bubble collisions on the microwave background radiation and other cosmological observables.
• Work on the fundamental origin of cosmic inflation.
• Demonstrating that theories with multiple axion fields can account for many otherwise mysterious features of our universe.