The book "The Caspian Sea Environment" provides a comprehensive systematic description of knowledge regarding the physical oceanography, marine chemistry, pollution, and marine biology of the Caspian Sea. It highlights the characteristic features of the sea's environmental conditions and their changes in the second half of the 20th century. The current challenges facing the Caspian Sea, particularly the interannual changes in sea level and the assessment of chemical pollution and its impacts on the biota, are discussed in detail. Additionally, special attention is given to the socioeconomic, legal, and political aspects of the region. The content is based on extensive observational data collected during sea voyages, as well as archival data from several Russian oceanographic institutions and scientific literature, mostly published in Russian editions. This book is aimed at professionals working in various fields of oceanography, chemistry, environmental research, and biology.