Weymouthia is a genus of two species belonging to the feather mosses. Weymouthia occurs in southern South America, New Zealand and south-eastern Australia and Lord Howe Island. It is characterised by (i) its monopodial, often hanging growth form; (ii) slight differences between stem and branch leaves; and (iii) the straight perichaetial leaves. In contrast to other genera in the Lembophyllaceae, secondary stems appear unable to arch back to the substrate and then root and form a new creeping stem.<ref name="Klazenga"/>
Weymouthia was named in honour of William Anderson Weymouth (1842–1932), a prominent Tasmanian botanist.<ref name="Klazenga"/> The species epithet mollis meaning soft, flabby, weak or feeble in Latin, refers to the exclusively hanging branches in this species. The species epithet cochlearifolia refers to the spoon-shaped leaves that resemble those of scurvy-grass.
Weymouthia has traditionally been assigned to the Meteoriaceae, mainly because of the hanging branches. Later the genus was included in the Lembophyllaceae,<ref name="Klazenga"/> but according to recent cladistic analyses based on DNA, this family is polyphyletic, and its revision is to be expected.<ref>Template:Cite journal</ref>
Key to the species
|1||Leaves oblong, more than twice as long as wide; upper laminal cells not or shallowly pitted. → Weymouthia mollis|
|-||Leaves broadly ovate, less than twice as long as wide; upper laminal cells strongly pitted. → Weymouthia cochlearifolia<ref name="Klazenga"/>|