Myida (formerly Myoida) is an order of saltwater and freshwater clams, marine and freshwater bivalve molluscs in the subclass Heterodonta. The order includes such bivalves as soft-shell clams, geoducks and shipworms.

They are burrowing molluscs with well-developed siphons. The shell is relatively soft and lacks a nacreous layer. Some species have a single cardinal tooth.

Superfamilies and families within the Myida include (the use of † indicate taxa that are extinct):