Isoetes taiwanensis is a species of plant in the Isoetaceae family. It is endemic to Taiwan, and the only species of quillwort there. As other quillworts, it is a relatively small species, with erect leaves 7–24 cm (2.8–9.4 in) high. It grows in shallow ponds, submersed most of the year. IUCN considers it critically endangered because of habitat loss.