Macrostomorpha is a clade of free living flatworms ranked either as class or subclass in the group Rhabditophora.

There are about 260 described species in two orders - marine, freshwater and brackish Macrostomida, which group most of the species diversity, and exclusively marine Haplopharyngida with only three described species.

[1] Macrostomorpha constitute a basal group in Rhabditophora, showing such plesiomorphic condition as entolecithal eggs and spiral cleavage.

[2] Another trait found among members of the clade is presence of hard stylet in the male copulatory organ.

This flatworm- (or platyhelminth-) related article is a stub.