Quantum Cosmology

Invited contribution to the Encyclopedia of Mathematical Physics (2nd edition), providing an overview over some main ideas and results in quantum cosmology. Key points: Canonical quantisation of homogeneous, isotropic cosmology; discussion of ambiguities in this quantisation; Construction of explicit solutions, attempts at physical interpretation; conceptual issues (time evolution, unitarity, probability interpretation); Introduction of scalar fields or perfect fluids; Discussion of whether classical singularities are resolved; Addition of inhomogeneities, possible predictions for primordial cosmology; Connections to string theory and loop quantum gravity.