The book is written for specialists in the fields of fluid mechanics, applied mathematics, nonlinear physics, physical oceanography and geophysics, and also for students learning these subjects. It includes a wide range of observational data on rogue (or freak) waves in the seas and coastal waters, as well as presenting a basic statistical description of extreme water waves. The book describes the modern approaches, including theoretical and numerical models applied to explain the physical origin of such anomalous waves on the sea surface, taking into account wind flow above waves and also variable bathymetry and currents. Apart from these analytical and numerical approaches, laboratory experiments and in-situ observations are reported too.