First Published in 1992. This book arose as a result of the authors work on the review 'Solitary Vortices in Plasmas' written for the Soviet Journal of Plasma Physics. With the development of nonlinear wave theory some novel concepts came into use, such as solitary waves, solitary vortices, and solitons. There is still some inconsistency in the use of these terms. The study of solitary waves (solitons) should ultimately lead to a better understanding of the internal structure of elementary particles. That is why solitons are attracting great attention from physicists and mathematicians. The material presented in this book shows that solitons are also of interest in plasma physics and geophysics, where these concepts have many important applications.