Unionoida

Taxobox
name = Unionoida

---

image_caption = "Anodonta anatina"
regnum = Animalia
phylum = Mollusca
classis = Bivalvia
subclassis = Palaeoheterodonta
ordo = Unionoida
ordo_authority = Stoliczka, 1871
subdivision_ranks = Families
subdivision = See text.

Unionoida is an order within the class Bivalvia. Members of the order Unionoida, which includes the pearly freshwater mussels, are found on six continents. There are approximately 900 species.

Families in the Order Unionoida

* Etheriidae Swainson, 1840
* Margaritiferidae Haas, 1940
* Mutelidae Swainson, 1840
* Unionidae Fleming, 1828
* Hyriidae Swainson, 1840
* Mycetopodidae Gray, 1840