The birdwing pearlymussel (Lemiox rimosus) is a rare species of freshwater mussel in the family Unionidae, the river mussels. This aquatic bivalve is native to Tennessee and Virginia in the United States. Its range has declined over 90%. It is a federally listed endangered species of the United States. This mussel remains in three rivers in Tennessee and Virginia, the Duck, Clinch, and Powell Rivers, having been extirpated from many more. It is now extinct in the state of Alabama.