This volume is intended as a self-contained introduction to the basic notions of geometric group theory, the main ideas being illustrated with various examples and exercises. One goal is to establish the foundations of the theory of hyperbolic groups. There is a brief discussion of classical hyperbolic geometry, with a view to motivating and illustrating this. The notes are based on a course given by the author at the Tokyo Institute of Technology, intended for fourth year undergraduates and graduate students, and could form the basis of a similar course elsewhere. Many references to more sophisticated material are given, and the work concludes with a discussion of various areas of recent and current research.