Grammitidoideae is a subfamily of the fern family Polypodiaceae, whose members are informally known as grammitids. It comprises a clade of about 750 species. They are distributed over higher elevations in both the Old and New World. This group was previously treated as a separate family, Grammitidaceae until molecular phylogenies showed it to be nested within the Polypodiaceae. It has since been treated as an unranked clade within subfamily Polypodioideae (renamed tribe Polypodieae in one classification), and, most recently, as a separate subfamily (reducing Polypodioideae to an evolutionary grade).