This book deals with gradient-vorticity oceanic waves, defined as waves whose periods are much longer than the inertial period. The main subject of this book is to study the mechanisms that determine gradient-vorticity wave processes in the ocean. The book consists of an introduction and four parts. The first part deals with the fundamentals of the gradient-vorticity wave theory. Due to the development of satellite altimetry (ERS-1, ERS-2 and TOPEX/POSEIDON), there has been a lot of progress in the work studying low-frequency waves in the ocean. In the last 4 parts of the book the altimetry provides the base of most of the scientific investigation presented from the Southern, Pacific and Arctic Oceans. The description of gradient-vorticity waves begins with the Southern Ocean, where the meridional-boundary effects are small, but planetary and jet effects are most pronounced. In the Pacific, main attention is given to the trapped equatorial waves, Rossby waves, waves in jet streams, and low-frequency waves on the oceanic shelf. The last chapter presents results of studies of trapped low-frequency waves in the Siberian Shelf Seas.