Ranunculus hawaiensis is an erect or ascending perennial herb in the Ranunculaceae (buttercup) family, with stems 50 to 200 cm (1.6 to 6.6 ft) long, and with fibrous roots. Stems are densely covered with golden or whitish hairs. Basal leaves are twice compound, with irregularly toothed and lobed lanceolate leaflets (narrow oval shape tapering to a point at each end), 5 to 7 cm (2 to 2.8 in) long and 4 to 7 cm (1.6 to 2.8 in) wide, with the terminal leaf the largest. The small five-petaled, yellow, glossy flowers are numerous in branched open cymes (a flower cluster with a central stem bearing a single terminal flower that develops first, the other flowers in the cluster developing as terminal buds of lateral stems), and contain a scale covered nectary at the base. Achenes are 5 mm (0.2 in) long, margined with a narrow wing, pitted, and with a beak 0.9 to 1.2 mm (0.04 to 0.05 in) long. Ranunculus hawaiensis differs from R. mauiensis in the degree to which achenes are beaked and the length of the achene body.