The Petersen graph occupies an important position in the development of several areas of modern graph theory because it often appears as a counter-example to important conjectures. In this account, the authors examine those areas, using the prominent role of the Petersen graph as a unifying feature. Topics covered include: vertex and edge colourability (including snarks), factors, flows, projective geometry, cages, hypohamiltonian graphs, and symmetry properties such as distance transitivity. The final chapter contains a mixture of other topics in which the Petersen graph has played its part. Undergraduate students should profit from reading this book as there are few prerequisite skills involved, and it could be used for a second course in graph theory. At the same time, the authors have also included a number of unsolved problems as well as topics of recent study. It should, therefore, also be useful as a reference for graph theorists.