He will discuss the astrophysical evidence for massive, compact black objects in our universe, and the processes by which they can be formed. General relativity interprets these objects as black holes - regions of spacetime in which gravity becomes so strong that nothing can escape. He will explain the main features of their physics, as predicted by relativity and quantum theory, in non-technical language. Finally he will discuss, again in a non-technical way, some of the extraordinary properties of so-called supersymmetric black holes, which place them at the centre of current research in string theory and pure mathematics.