This book provides an up-to-date review of the fundamentals of sphingolipid metabolism and its role in metabolic diseases. Focusing on the sphingolipid de novo synthesis pathway, the effect of sphingomyelin, ceramide, and sphingosine-1-phosphate, and linkage between sphingolipids and other lipids, such as cholesterol, it covers serine palmitoyltransferase, ceramide synthases, ceramidases, sphingosine kinases, and sphingomyelin synthases, and more. While highlighting how rare diseases related to abnormal glycosphingolipid metabolism, this publication introduces sphingolipid metabolism-related diseases, such as lung diseases and cancers, as well as sphingolipid circadian regulation. The book demonstrates advances and limitations of research on sphingolipid metabolism and its roles in metabolic diseases and other diseases. It offers graduate students and researchers a coherent overview of sphingolipids, as well as the limitations of current research in the field, and promotes further studies on metabolic diseases, as well as pharmaceutical research on drug discovery based on sphingolipid de novo synthase.