Lipid nanoparticles (LNPs) or solid lipid nanoparticles (SLNs, sLNPs) are nanoparticles composed of lipids and possess a solid lipid core matrix which is able to solubilize lipophilic molecules. Typically they are spherical with an average diameter between 10 and 1000 nanometers.

Lipid nanoparticles have emerged across the pharmaceutical industry as promising vehicles to deliver a variety of therapeutics.  They are a novel pharmaceutical drug delivery system and formulation. LNPs became more widely known in late 2020, as some COVID-19 vaccines that use RNA vaccine technology coat the fragile mRNA strands with PEGylated lipid nanoparticles as their delivery vehicle.

Liposomes, an early version of LNPs, are a versatile nanomedicine delivery platform. A number of liposomal drugs have been approved and applied to medical practice. A liposome is a spherical vesicle with at least one lipid bilayer. The liposome can be used as a vehicle for administration of nutrients and pharmaceutical drugs. Liposomes are composite structures, consisting of phospholipids, especially phosphatidylcholine. It may contain small amounts of other molecules. Though liposomes can vary in size from low micrometer range to tens of micrometers, unilamellar liposomes, shown as the Figure below, are typically in the lower size range with various targeting ligands. The ligands are attached to their surface allowing for their surface-attachment and accumulation in pathological areas for treatment of disease.