The oxysterol-binding protein (OSBP)-related proteins (ORPs) are a family of lipid transfer proteins (LTPs). Concretely, they constitute a family of sterol and phosphoinositide binding and transfer proteins in eukaryotes that are conserved from yeast to humans. They are implicated in many cellular processes related with oxysterol, including signaling, vesicular trafficking, lipid metabolism, and nonvesicular sterol transport.