Effective field theories are a widely used tool in various branches of physics. This book provides a comprehensive discussion of the foundations and fundamentals of effective field theories of quantum chromodynamics (QCD) in the light quark sector with an emphasis on the study of flavour symmetries and their realizations. In this context, different types of effective field theories pertaining to various energy scales are considered and selected applications are devised. It also covers the formulation of effective field theories in a finite volume and its application in the analysis of lattice QCD data. Effective Field Theories is intended for graduate students and researchers in particle physics, hadron physics and nuclear physics. Exercises are included to help the reader deepen their understanding of the topics discussed throughout, with solutions available to lecturers.