Euphorbia eleanoriae, a member of the Euphorbiaceae (spurge) family, is a small shrub endemic to Kauai. It has brittle, dense erect-ascending (growing upward) branches, and dark gray basal stems. The leaves are elliptical to broadly ovate, with blades 10 to 20 mm (0.4 to 0.8 in) long and 6 to 14 mm (0.2 to 0.6 in) wide. The leaves are usually pale green, sometimes with a reddish tint on the margins and are oppositely arranged with each succeeding pair set at right angles to the previous pair, or sometimes spirally arranged. The inflorescences (flowering clusters) are cyathia (containing unisexual flowers without petals) that are borne either solitary or at the terminal branch tips. The styles and stamens are dark purple. The fruit is a capsule, green with a purple-red apex, and the seeds are 2.2 mm (0.09 in) long and 1.3 mm (0.05 in) in diameter.