NPC1L1 (of: Niemann-Pick C1 -like protein 1), the protein in the cell membrane to facilitate the transport of cholesterol, phytosterols and other lipids in the cell. It is a transporter, with the way the import is not yet fully understood. NPC1L1 is formed in mammals in many tissue types in humans, especially in the liver and small intestine enterocytes (where it is mainly responsible for the absorption of cholesterol from food), but also in the pancreas, kidney, lung, spleen, heart, gall bladder, brain, testis, stomach and muscles.

NPC1L1 is the target of the drug ezetimibe and is completely inactivated by him. Mutations in NPC1L1 gene are likely to be responsible for resistance to ezetimibe.