This book presents a self-contained account of the exact solution of the Hubbard model in one dimension. The description of solids at a microscopic level is complex, involving the interaction of a huge number of its constituents. It is impossible to solve the corresponding many-body problems, although insight can be gained from analysis of simplified models. An important example is the Hubbard model, which describes interacting electrons in narrow energy bands and which has been applied to a diverse range of problems.