Amborella is a monotypic genus of understory shrubs or small trees endemic to the main island, Grande Terre, of New Caledonia in the southwest Pacific Ocean.

[5] The genus is the only member of the family Amborellaceae and the order Amborellales and contains a single species, Amborella trichopoda.

[6][7] The leaves are two-ranked, with distinctly serrated or rippled margins, and about 8 to 10 centimetres (3 to 4 inches) long.

[11] The small, creamy white flowers are arranged in inflorescences borne in the axils of foliage leaves.

An anther consists of four pollen sacs, two on each side, with a small sterile central connective.

[4][20] Currently plant systematists accept Amborella trichopoda as the most basal lineage in the clade of angiosperms.

Since Amborella is apparently basal among the flowering plants, the features of early flowering plants can be inferred by comparing derived traits shared by the main angiosperm lineage but not present in Amborella.

One early 20th century idea of "primitive" (i.e. ancestral) floral traits in angiosperms, accepted until relatively recently, is the Magnolia blossom model.

In a study designed to clarify relationships between well-studied model plants such as Arabidopsis thaliana, and the basal angiosperms Amborella, Nuphar (Nymphaeaceae), Illicium, the monocots, and more derived angiosperms (eudicots), chloroplast genomes using cDNA and expressed sequence tags for floral genes, the cladogram shown below was generated.

[21] Acrogymnosperms Amborella Nuphar Illicium monocots magnoliids eudicots This hypothesized relationship of the extant seed plants places Amborella as the sister taxon to all other angiosperms, and shows the gymnosperms as a monophyletic group sister to the angiosperms.

[28] Amborella, being an understory plant in the wild, is commonly in intimate contact with shade- and moisture-dependent organisms such as algae, lichens and mosses.

[10] The islands of New Caledonia are a biodiversity hot-spot, preserving many early diverging lineages of plants, of which Amborella is but one.

Current threats to biodiversity in New Caledonia include fires, mining, agriculture, invasion by introduced species, urbanization and global warming.

[24] The importance of conserving Amborella has been dramatically stated by Pillon: "The disappearance of Amborella trichopoda would imply the disappearance of a genus, a family and an entire order, as well as the only witness to at least 140 million years of evolutionary history.