This book offers a clear introduction to the key theoretical concepts needed to explore modern research topics in quantum fluids, with a particular focus on solitons and vortices. It is designed for graduate students and junior researchers, who want to build the foundation required to engage with current work in the field. The text begins with a brief historical overview before moving on to particle statistics, weakly interacting condensates and their dynamics, and both linear and nonlinear excitations—including solitons and vortices. It also covers superfluid helium and the physics of quantum turbulence. This second edition expands and updates the material to reflect major developments in the last decade. New chapters introduce readers to two-component condensates, dipolar condensates, quantum droplets and supersolids, vortex reconnections, and modern studies of quantum turbulence. The distinction between two-dimensional and three-dimensional turbulence is now treated explicitly, together with comparisons between classical (ordinary-fluid) turbulence and quantum turbulence. As with the first edition, each chapter includes exercises. This edition also provides complete solutions at the end of the book, making it well suited for self-study or course adoption.