Les Houches lectures on two-dimensional gravity and holography

Lecture notes prepared for the Les Houches school ‘‘Quantum Geometry: Mathematical Methods for Gravity, Gauge Theories and Non-Perturbative Physics’’ that took place during the summer 2024. We cover the techniques to perform the exact gravitational path integral of two-dimensional dilaton-gravity, and supergravity, over spacetimes with arbitrary topology, with an application to black holes. We discuss the connection with random matrix models and moduli spaces of hyperbolic surfaces briefly, since those concepts were covered in other lectures of the school.