This chapter examines advances in understanding lipid requirements and utilisation in dairy cattle. The chapter begins by first highlighting the major lipid constituents found in dairy cow nutrition, such as free fatty acids, triglycerides, glycolipids and phospholipids. It then goes on to discuss lipid supplements, which is then followed by an examination of fat digestion and absorption in ruminant species. Sections on digestibility of dietary lipids and mammary metabolism of lipids are also provided. The chapter discusses the effects of lipids on feed intake as well as the effects of lipid supplements on milk production on composition. This is then followed by an overview of how dietary lipids can be used to modify milk fat for human health, as well as the effects of lipids on reproduction. The role of dietary lipids in metabolism regulation is also reviewed, followed by an analysis of the important considerations that should be taken into account when selecting for commercial inert fats. Practical recommendations for supplementing fats are also included.