This timely book introduces the subject of Fluid-Structure Interactions (FSI) to students and professionals. It discusses the major ideas in FSI with the goal of providing the fundamental understanding to the readers who possess limited or no understanding of the subject. The author presents the physics of the problem, rather than focusing on the methods, and discusses the essential methods of analysis. The principle goal of Introduction to Fluid-Structure Interactions is impart to students and practitioner a physical understanding of major topics in fluid-structure interactions: axial flow problems (when the direction of the flow is parallel to the long axis of the structure) and crossflow problems (when the direction of the flow is normal to the long axis of the structure). Facilitating readers' understanding of both categories, starting with simple 1 DOF systems and continuing to more complicated continuous flexible structures, this book is ideal for graduate students and practitioners interested in this critical field. It stands as a unique introductory volume to study Fluid-Structure Interactions (FSI);Covers aspects of FSI relevant to Fluid Mechanics, Wind Energy, Ocean Engineering, and Biomedical research; integrates most recent findings from research on FSI; emphasizes the physics behind the phenomena in detail; and maximizes readers understanding by beginning with fundamental concepts and developing focus to more complex systems.