Eutrema japonicum is a perennial rhizomatous plant in the mustard family (Brassicaceae) best known as the primary botanical source of true wasabi. The genus name Eutrema derives from Greek eu meaning “well” and trema meaning “hole”, referring to hole found in the septum of the plant's fruiting pods, while the species epithet japonicum means “of Japan”. The plant has historically also been classified under the synonym Wasabia japonica. Native to cool, shaded mountain stream valleys of Japan and parts of the Korean Peninsula and eastern Russia, it thrives in running, well-oxygenated water and high-humidity environments.

Eutrema japonicum produces broad, heart-shaped leaves and a thickened rhizome, the latter being the prized culinary portion. Historically and in modern usage, the freshly grated rhizome is consumed as wasabi, a pungent condiment traditionally paired with sushi and sashimi in Japan. Unlike many dried or powdered commercial “wasabi” products, which often contain horseradish (Armoracia rusticana) and mustard, authentic wasabi derives from this species and is valued for its more complex, fleeting pungency and subtle sweetness. The plant’s characteristic sharpness arises from enzymatic hydrolysis of glucosinolates when the tissue is disrupted, forming volatile isothiocyanates. The entire plant is edible, so leaves and stems are sometimes pickled or incorporated into regional dishes.

Significant bioactive compounds include specific glucosinolates such as sinigrin and related precursors that convert to allyl isothiocyanate and other isothiocyanates, compounds associated with antimicrobial activity and potential chemoprotective effects in experimental research. The plant is most culturally significant in Japanese gastronomy, where traditional cultivation methods in flowing stream beds (sawa wasabi) are considered the highest quality form of production.