Foundations of Geophysical Electromagnetic Theory and Methods, Third Edition provides a comprehensive treatment of electromagnetic (EM) theory and its applications in geophysics. This updated edition incorporates more than a decade of advances in theoretical developments, numerical modeling, and practical EM surveying while maintaining the clarity and rigor of previous editions. The book begins with an introduction to field theory, including the differential calculus of vector fields and foundational principles underlying classical electromagnetic formulations. It then reviews the core elements of EM theory, covering Maxwell&s equations, models of EM induction in the Earth, and the behavior of electromagnetic fields in heterogeneous media. Subsequent chapters address the inversion and imaging of EM data, discussing the theory of ill-posed inverse problems, regularization strategies, electromagnetic inversion methodologies, and migration techniques used to construct subsurface images. The volume then turns to applied geophysical methods, examining the electromagnetic properties of rocks and minerals, the generation and measurement of EM fields, and survey techniques across a range of domains, including direct current, induced polarization, natural-field EM, controlled-source EM, and marine and airborne EM methods. A set of case studies illustrates the practical use of EM methods in geophysics, including mineral and energy resource exploration. Presents theoretical and methodological foundations of geophysical field theory Illustrates the current state-of-the-art in EM geophysical technology Discusses the practical aspects of EM exploration for mineral and energy resources, including a variety of diverse case studies.