Ptychobranchus occidentalis is a species of freshwater mussel in the family Unionidae, the river mussels.

It is endemic to the United States,[1] where it is known from Arkansas, Kansas, Louisiana, Missouri, and Oklahoma.

Its common name is Ouachita kidneyshell.

[2] This mussel packages its larvae, or glochidia, in a membranous conglutinate which resembles a small prey item.

When a fish comes to investigate this lure, the glochidia attach to its gills and use it as a host during their development.