Hymenophyllum is a genus of ferns in the family Hymenophyllaceae.

Its name means "membranous leaf", referring to the very thin translucent tissue of the fronds, which gives rise to the common name filmy fern for this and other thin-leaved ferns.

The leaves are generally only one cell thick and lack stomata, making them vulnerable to desiccation.

Consequently, they are found only in very humid areas, such as in moist forests and among sheltered rocks.

As of October 2022[update], World Ferns accepted the following extant species:[2] H. scabrum A.Rich.

(Shiny filmy fern) H. rufescens Kirk H. cruentum Cav.

(Helecho película) H. asplenioides (Sw.) Sw. H. heimii Tardieu H. paniense Ebihara & K.Iwats.

(Kidney fern) H. fuciforme Sw. H. pulcherrimum Colenso H. badium Hook.

(Pallante chilote) H. pluviatile Perrie & Brownsey H. australe Willd.

H. gracilescens Domin H. imbricatum Blume H. javanicum Spreng.

H. tomentosum Kunze H. digitatum (Sw.) Fosberg H. nitidulum (Bosch) Ebihara & K.Iwats.

H. ferrugineum Colla H. poolii Baker H. rufum Fée H. trichophyllum Kunth H. plumosum Kaulf.

H. cocosense A.Rojas H. hirsutum (L.) Sw. H. crassipetiolatum Stolze H. crispum Kunth H. delicatulum Sehnem H. ivohibense Tardieu H. splendidum Bosch H. fragile (Hedw.)

Morton H. latifrons Bosch H. elegans Spreng.

ex Kuhn H. wrightii Bosch H. bryoides C.W.Chen, Ebihara & K.Y.Cheng H. fujisanense Nakai H. polyanthos (Sw.) Sw. (Smooth filmy fern) H. punctisorum Rosenst.

H. parallelocarpum Hayata H. armstrongii (Baker) Kuhn H. marginatum Hook.

H. perrieri Tardieu H. ectocarpon Fée H. peltatum (Poir.)

(Wilson´s filmy fern) H. triangulare Baker H. cupressiforme Labill.

(Common filmy fern) H. pumilum C.Moore H. baileyanum Domin H. blandum Racib.

ex Kuhn H. soriemersum Rouhan & C.Del Rio H. macgillivrayi (Baker) Copel.