In zoological nomenclature, a subphylum is a taxonomic rank below the rank of phylum.
The taxonomic rank of "subdivision" in fungi and plant taxonomy is equivalent to "subphylum" in zoological taxonomy. Some plant taxonomists have also used the rank of subphylum, for instance monocotyledons as a subphylum of phylum Angiospermae and vertebrates as a subphylum of phylum Chordata.
Where convenient, subphyla in turn can be divided into infraphyla; in turn such an infraphylum also would be superordinate to any classes or superclasses in the hierarchy.
Not all fauna phyla are divided into subphyla. Those that are include:
Examples of infraphyla include the Mycetozoa, the Gnathostomata and the Agnatha.