Botrychium lunaria is a species of fern in the family Ophioglossaceae<ref name="Christenhusz_2011b">Template:Cite journal</ref> known by the common name moonwort<ref name=BSBI07>Template:Cite web</ref> or common moonwort. It is the most widely distributed moonwort, growing throughout the Northern Hemisphere across Eurasia and from Alaska to Greenland, as well as temperate parts of the Southern Hemisphere.
This is a small plant growing up to 30cm in height<ref name=Stace>Template:Cite book</ref>Template:Rp from an underground caudex. The leaf is pinnate and unique in being divided into a sterile frond and a fertile frond. The sterile frond of the leaf has 4 to 9 pairs of fan-shaped leaflets or pinnae. The fertile part of the leaf is very different in shape, with rounded, grapelike clusters of sporangia producing spores by which it reproduces. As in other members of the family Ophioglossaceae, this species is eusporangiate, the sporangia derived from more than one initial cell and having sporangial walls more than one cell thick. Their spores develop into underground, mycotrophic gametophytes.<ref name=Stace/> Moonworts die down at the end of summer, frequently lying dormant for several seasons before re-appearing.<ref name="Jermy">The Illustrated Field Guide to Ferns and Allied Plants of the British Isles; Jermy & Camus; First edition; 1991</ref>
Moonwort has a circumpolar distribution, being recorded in Eurasia, North America and Greenland.<ref name=DVF>Template:Cite web</ref> It also occurs in north Africa, the Himalayas, and temperate zones of Australia, Tasmania, New Zealand and South America.<ref name=IUCN>Template:Cite web</ref><ref name="Welsh Ferns">Welsh Ferns; Hutchinson & Thomas; Seventh edition; 1996</ref> Although its distribution is patchy, and it may be locally rare, it is rated as of least concern in The IUCN Red List of threatened species.<ref name=IUCN/> There is evidence of some decline in the British Isles,<ref name=BRC_BSBI>Template:Cite web</ref> and in Ukraine, 189 loci were recorded, 118 before 1980, 58 after 1980 and 13 after 1980.<ref>Template:Cite web</ref>