Strongylocentrotus intermedius, commonly known as the northern sea urchin or short-spined sea urchin, is a marine echinoderm in the family Strongylocentrotidae. It is native to the cold temperate waters of the northwest Pacific Ocean, particularly along the coasts of northern Japan (especially Hokkaido), the Russian Far East, and parts of the Sea of Okhotsk. The genus name Strongylocentrotus derives from Greek strongylos meaning “round” and kentron meaning “spine,” referring to the spherical body covered in spines. The species epithet intermedius is Latin for “intermediate,” likely indicating its size compared with related species. It inhabits rocky coastal substrates and kelp forests, where it grazes primarily on macroalgae.

Historically, sea urchins have been harvested in northern Japan and adjacent regions for their edible gonads, and in modern contexts Strongylocentrotus intermedius is commercially fished and also cultivated through aquaculture in Japan and China. As a food source, Strongylocentrotus intermedius is valued for its gonads, known in Japanese as uni. The edible portion consists of five bright orange to yellow lobes with a creamy texture and briny-sweet, umami-rich flavor. It is most commonly consumed raw as sushi or sashimi in Japan, where it is considered a delicacy, but it may also be used in rice bowls, pasta, soups, or lightly cooked dishes. In Hokkaido, high-quality uni from this species is especially prized. Harvesting is typically seasonal to ensure optimal gonad development and flavor, which are influenced by diet and reproductive cycle. In sushi, it is served atop vinegared rice, while in contemporary cuisine it may be incorporated into creamy sauces or seafood preparations.

Strongylocentrotus intermedius contains omega-3 fatty acids such as eicosapentaenoic acid (EPA), Vitamin A/carotenoids such as echinenone and β-carotene, vitamin E (tocopherols), and high-quality marine proteins and free amino acids such as glycine and alanine that contribute to sweetness and flavor. As a marine invertebrate, Strongylocentrotus intermedius may accumulate environmental contaminants depending on habitat quality, but when sourced from clean waters it is regarded as a nutrient-dense and culturally significant seafood in northern Pacific cuisines.