Quillaja is a genus of flowering plants, the only extant genus in the family Quillajaceae with two or three known species.

[1] It was once thought to be in the rose family, Rosaceae,[2] but recent research shows it belongs in its own family.

The inner bark of the soap bark tree (Q. saponaria) contains saponin, which is a natural soap.

Members of this genus are trees that grow to about 25 metres (82 ft).

The species were revised by Federico Luebert in 2014:[3]