In this book the author extends the concepts previously introduced in his "Quantum Field Theory in Condensed Matter Physics" to situations in which the strong electronic correlations are crucial for the understanding of the observed phenomena. Starting from a model field theory to illustrate the basic ideas, more complex systems are analysed in turn. A special chapter is devoted to the description of antiferromagnets, doped Mott insulators and quantum Hall liquids from the point of view of gauge theory. This advanced text is written for graduate students and researchers working in related areas of physics.