As of September 2016, the International Union for Conservation of Nature (IUCN) lists 1988 data deficient mollusc species. 27% of all evaluated mollusc species are listed as data deficient. The IUCN also lists 40 mollusc subspecies as data deficient. No subpopulations of molluscs have been evaluated by the IUCN. This is a complete list of data deficient mollusc species and subspecies evaluated by the IUCN.