Utterbackia imbecillis, commonly called the paper pondshell, is a species of freshwater mussel, an aquatic bivalve mollusk in the family Unionidae, the river mussels.
It is characterized by its unusually thin shell.
This species is native to the United States. It is present in the Mississippi interior basin, western and eastern gulf, and the Atlantic Slope drainages. It is a common and widespread species. Thousands of individuals can inhabit a single pond.