The Platyzoa ("flat animals") are a group of protostomes proposed by Thomas Cavalier-Smith in 1998. This is a taxon above the level of phylum, and is not part of the usual system of classification.

Cavalier-Smith included here the Platyhelminthes (flatworms), and a new phylum Acanthognatha, into which he gathered several previously described phyla of microscopic animals. Subsequent studies have supported Platyzoa as a viable clade, while differing on the phyla included and on relationships within Platyzoa.