The nucleon optical model is widely used to calculate the elastic scattering cross-sections and polarisations for the interaction of neutrons and protons with atomic nuclei. The optical model potentials not only describe the scattering but also provide the wave functions needed to analyse a wide range of nuclear reactions. They also unify many aspects of nuclear reactions and nuclear structure. This book consists of a comprehensive introduction to the subject and a selection of papers by the author describing the optical model in detail. It contains full references to the original literature with many examples of the application of the model to the analysis of experimental data.