After briefly reviewing motivations for string theory as a candidate UV completion of gravity and particle physics, I will survey its interface cosmological physics. Extrapolating general relativity to asymptotically early times leads to would-be singularities smoothed by string-theoretic corrections, such as winding string condensates. Although conceptually interesting, much of this physics may be screened by inflation in the most promising scenario for observable cosmology. The talk will then turn to an overview of models of inflation in string theory, including new mechanisms with distinctive predictions. The talk will conclude with a brief discussion of models of the cosmological constant obtained by stabilizing the extra dimensions of string theory via a balance of forces, and the challenges that ensue.