Niemann–Pick disease (/niːmənˈpɪk/ nee-mən-PIK) is a group of inherited severe metabolic disorders in which sphingomyelin accumulates in lysosomes in cells. The lysosomes normally transport material through and out of the cell.

The prognosis is individual but the severe form is fatal in toddlerhood and the milder forms may even in some cases have a normal lifespan.