Iron is an essential nutrient for most organisms; however, it can also be toxic when present in excess. For this reason, life has evolved complex pathways to tightly control the amount of iron contained within body tissues. Unlike most other nutrients, mammals do not have a regulated excretory mechanism for iron and, therefore, must regulate body iron levels at the point of dietary iron absorption in the proximal small intestine. In this chapter, we will describe the molecules and pathways involved in this important process, including our current understanding of the mechanisms of both heme and non-heme iron absorption. The regulation of this process will also be discussed, with particular emphasis on local and systemic factors that affect how much iron is absorbed from the diet. We also highlight areas where our knowledge is incomplete and where more research is required to fully understand the molecular mechanisms responsible for this essential process.