Pinnotheridae is a family of tiny soft-bodied crabs that live commensally in the mantles of certain bivalve molluscs and the occasional large gastropod mollusc species in genera such as Strombus and Haliotis. Tunicotheres moseri is commensal with a tunicate. The earliest fossils attributable to the Pinnotheridae date from the Danian.
The following genera are recognised in the family Pinnotheridae: