Marianthus is a genus of flowering plants in the family Pittosporaceae and is endemic to Australia.

Plants in the genus Marianthus are shrubs with twining branches, simple leaves arranged alternately along the stems.

Plants in this genus were previously included in Billardiera, but have a stalked ovary and a long, usually curved style.

The genus Marianthus was first originally established in 1837 by Stephan Endlicher in his Enumeratio plantarum quas in Novae Hollandiae ora austro-occidentali ad fluvium Cygnorum et in sinu Regis Georgii collegit Carolus Liber Baro de Hügel, and the first species he described (the type species) was M. candidus.

[2] The name Marianthus means "Virgin Mary-flower", on account of the white colour of M. candidus, the first species in the genus to be described.