This comprehensive and self-contained exposition of the algebro-geometric theory of singularities of plane curves covers both the classical and modern aspects of the field. It gives a unified treatment with complete proofs and presents modern results which have only appeared in research papers. It updates and correctly proves a number of important classical results for which there was formerly no suitable reference. With new, previously unpublished results as well as applications to algebra and algebraic geometry, this book will be useful as a reference text for researchers in the field. It is also suitable as a textbook for postgraduate courses on singularities.