Alphitonia is an arborescent genus of flowering plants with about 20 species, belonging to the buckthorn family (Rhamnaceae) of the rosid eudicots. It occurs in tropical regions of Southeast Asia, Oceania and Polynesia. These are large trees or shrubs. In Australia, these plants are often called "ash trees" or "sarsaparilla trees". This is rather misleading however; among the flowering plants, Alphitonia is not closely related to the true ash trees (Fraxinus of the asterids), and barely at all to the monocot sarsaparilla vines (Smilax).
The name is derived from a Greek word meaning "pearl barley".
The lanceolate coriaceous leaves are alternate, about 12 cm long. The margins are smooth. Venation is pinnate. They have white to rusty complex hairs on the under surface. The petiole is less than a quarter the length of a blade. Stipules are present.
The small flowers form terminal or axillary clusters of small creamy blossoms during spring. The flowers are bisexual. Hypanthium is present. The flowers show 5 sepals, 5 petals and 5 stamens. The ovary is inferior. The fruits are ovoid, blackish non-fleshy capsules, with one seed per locule.
Alphitonia species are used as food plants by the larva the hepialid moth Aenetus mirabilis, which feed only on these trees. They burrow horizontally into the trunk, then vertically down.