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 and intrapetiolar stipules. The inflorescences are simple racemes 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 and one aluminum hyperaccumulator, Geissois polyphylla.