The ferns are a group of vascular plants, spores, which form the sister group of seed plants. The ferns include all vascular plants except the spores Lycopodiopsida: the horsetails, Psilotaceae, Ophioglossum, and Pteridopsida Marattiopsida. They are often referred to as Monilophyten, terms Monilophyta or Moniloformopses are no valid taxon names.

Worldwide there are about 12,000 species. In Central Europe, about 200 species are housed.