This book is the first to develop a unified gauge theory of condensed matter systems dominated by vortices or defects and their long-range interactions. Gauge fields provide the only means of describing these interactions in terms of local fields, rendering them accessible to standard field theoretic techniques. Two particularly important examples, superfluid systems and crystals, are treated in great detail. The theory is developed in close contact with physical phenomena and evolves naturally from conventional descriptions of the systems. In addition to gauge fields, the book introduces the important new concept of disorder fields for ensembles of line-like defects. The combined field theory allows for a new understanding of the important phase transitions superfluid 'normal and solid' liquid. Apart from the above, the book presents the general differential geometry of defects in spaces with curvature and torsion and establishes contact with the modern theory of gravity with torsion. This book is written for condensed matter physicists and field theorists. It can be used as a textbook for a second-year graduate course or as supplementary reading for courses in the areas of condensed matter and solid state physics, statistical mechanics, and field theory.