- a South American tree (Quillaja saponaria) of the rose family, with leathery leaves and white flower clusters
- its inner bark, used in cleansing preparations for its saponin content
- any of several tropical American trees (genus Pithecellobium) of the mimosa family, whose bark contains saponin
- A Chilean evergreen tree (Quillaja saponaria) of the rose family, having bark used as soap and as a source of saponin.
- The bark of this tree.