The chapter “Basic Notions of Naval Structure” introduces the fundamental principles that govern the structural behavior of ships and offshore platforms, emphasizing the types of loads acting on these constructions and the key methods used in their structural analysis. It classifies loads into gravitational, buoyancy, environmental, and operational, explaining their origins, characteristics, and relevance for design and safety. The chapter also presents essential concepts of naval structural calculation, including light ship displacement, hull girder theory, bending moment, and shear force, which describe how ships respond to internal and external stresses. Furthermore, it discusses the global structural analysis of vessels using simplified “box girder” models to evaluate longitudinal strength under conditions such as hogging and sagging. Through these foundational topics, the chapter provides a clear understanding of how engineers assess the strength, stability, and durability of naval and offshore structures throughout their service life.