Diadema setosum is a species of long-spined sea urchin in the family Diadematidae, commonly known as the long-spined sea urchin or black long-spined urchin. It is widely distributed throughout the Indo-Pacific region, ranging from the Red Sea and eastern coast of Africa to Japan, Australia, and many Pacific islands, where it inhabits coral reefs, rocky substrates, and seagrass beds in shallow marine waters. The genus name Diadema derives from the Greek diadēma, meaning “crown” or “diadem,” referring to the radiating arrangement of its long spines, while the species epithet setosum comes from the Latin setosus, meaning “full of bristles”.

Although more commonly recognized for its ecological role in grazing algae on coral reefs, Diadema setosum is also consumed as a food source in parts of Southeast Asia, the Pacific Islands, and occasionally in Japan, where its gonads are harvested as a form of uni. Its culinary use is generally more localized and less commercially developed than that of temperate sea urchin species, but it remains culturally significant in certain coastal subsistence and artisanal fisheries. As a food source, Diadema setosum produces edible gonads that may be consumed raw, lightly cooked, eaten with rice or incorporated into seafood dishes in Indo-Pacific coastal cuisines. It is associated with maritime food traditions in regions such as the Philippines, Indonesia, Micronesia, and parts of southern Japan.

Nutritionally, the species contains omega-3 fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). It also contains echinochrome A, a naphthoquinone pigment with antioxidant properties, ovothiol, a sulfur-containing antioxidant molecule found in marine invertebrates, and carotenoids such as β-carotene that contribute to pigmentation and potential antioxidant effects. However, Diadema setosum possesses venomous spines containing bioactive proteins and other toxic components that can cause painful envenomation if mishandled, making careful preparation essential when harvested for consumption.