The study of directed graphs has developed enormously over recent decades, yet no book covers more than a tiny fraction of the results from more than 3000 research articles on the topic. Digraphs is the first book to present a unified and comprehensive survey of the subject. In addition to covering the theoretical aspects, including detailed proofs of many important results, the authors present a number of algorithms and applications. The applications of digraphs and their generalisations include, among other things, recent developments in the Travelling Salesman Problem, genetics and network connectivity. More than 700 exercises and 180 figures will help readers to study the topic. Detailed indexes ease " navigation " through the book. Many open problems and conjectures will inspire further research. The topics vary from classical ones such as distances, flows in networks and hamilonicity to more recent ones such as connectivity augmentation, degree constrained orientations, linkings in digraphs, sub-modular flows, the even cycle problem and edge-colours graphs and digraphs. Algortihmic aspects are strongly emphasised throughout. This book will be essential reading and reference for all undergraduate students, graduate students and professionals in mathematics, operational research, computer science and other areas who are interested in graph theory and ifs applications.