This review by Douglas R. Tocher provides an in-depth analysis of the metabolism and functions of lipids and fatty acids in teleost fish. Lipids, along with proteins, are major organic constituents of fish, playing crucial roles in energy production, growth, reproduction, and movement. The review highlights the importance of long-chain, highly unsaturated fatty acids (ω3 HUFA) in fish lipids, which are vital for both fish and human nutrition. The article covers various aspects of lipid biochemistry, metabolism, and functions in fish, emphasizing the relevance of these processes in both natural and farmed environments. It discusses the digestion, absorption, and transport of lipids, as well as the biosynthesis and catabolism of fatty acids. The review also explores the roles of lipids in energy production, membrane structure, eicosanoid synthesis, and transcriptional control of lipid homeostasis. Additionally, it addresses the increasing application of molecular technologies in understanding fish lipid metabolism, including genomics and proteomics. The review concludes by highlighting areas that require further investigation and the potential of molecular biological and genetic techniques to advance the field.This review by Douglas R. Tocher provides an in-depth analysis of the metabolism and functions of lipids and fatty acids in teleost fish. Lipids, along with proteins, are major organic constituents of fish, playing crucial roles in energy production, growth, reproduction, and movement. The review highlights the importance of long-chain, highly unsaturated fatty acids (ω3 HUFA) in fish lipids, which are vital for both fish and human nutrition. The article covers various aspects of lipid biochemistry, metabolism, and functions in fish, emphasizing the relevance of these processes in both natural and farmed environments. It discusses the digestion, absorption, and transport of lipids, as well as the biosynthesis and catabolism of fatty acids. The review also explores the roles of lipids in energy production, membrane structure, eicosanoid synthesis, and transcriptional control of lipid homeostasis. Additionally, it addresses the increasing application of molecular technologies in understanding fish lipid metabolism, including genomics and proteomics. The review concludes by highlighting areas that require further investigation and the potential of molecular biological and genetic techniques to advance the field.