Isoetes engelmannii, commonly known as Engelmann's quillwort or Appalachian quillwort (not to be confused with the newly described Isoetes appalachiana), is an aquatic pteridophyte and is the most widely distributed species of its genus in eastern North America. Its range extends from Ontario in the north, south to Florida and west Arkansas and Missouri. It can be found from April to October in temporary pools, bogs, marshes, stream edges, swamps and along wet roadsides.