Geissois is a genus of trees and shrubs in the plant family Cunoniaceae. It includes about 19 species mostly found in New Caledonia, but also in Fiji, Vanuatu, and the Solomon Islands. Leaves are opposite, palmate with 3-9 leaflets, with entire margin (serrate in Geissois hirsuta and juveniles) and intrapetiolar stipules. The inflorescences are simple racemes (trident in Geissois hirsuta) and bottle-brush like. The flowers have four red sepals, lacking petals, with many long red stamens. The fruit is a capsule, the seeds flat and winged. The genus includes several nickel hyperaccumulator (most species occurring on ultramafic rocks) and one aluminum hyperaccumulator, Geissois polyphylla.