Shrubs, dense, erect, to 1 m. Stem segments dark green, flattened, elliptic, (4-)10-17.5 × (3-)5-7 cm, moderately tuberculate, making margins appear scalloped, glabrous; areoles 3-5 per diagonal row across midstem segment, elliptic to subcircular, 4-6 × 2.5-3 mm; wool pale tan to white, loose. Spines 2-3(-5) per areole, spreading, yellowish, aging gray-white; major ones straight, stout, slightly flattened, commonly spirally twisted, longest to 25-60 mm. Glochids dense in crescent at adaxial edge of areole, sparser along sides of areole, yellow, turning red to brown, to 5 mm. Flowers: inner tepals yellow throughout, to 30 mm; filaments and anthers pale yellow; style pale greenish yellow; stigma lobes pale cream. Fruits reddish at maturity, obovoid, 40 × 25 mm, fleshy, glabrous; areoles 17-21, bearing few spines to 9 mm. Seeds tan, subcircular, ± 3 mm diam.; girdle to 0.3 mm. 2n = 22 (Puerto Rico).

Flowering year-round. Brushlands, coastal sands, ocean bluffs, disturbed areas; 0 m; Fla.; West Indies.

Opuntia cubensis is known in the flora only on Big Pine Key, Florida.