The highly prized fatty tuna belly used as a luxury sushi topping is otoro. In Japanese sushi terminology, otoro is the fattiest portion of toro, cut from the belly and underside of tuna, especially bluefin tuna.
Because this area stores substantial fat, otoro has a pale, marbled appearance and a rich, buttery texture. Its high fat content makes it especially tender and gives it a flavor that is more luxurious than lean tuna cuts. The best pieces are often served as nigiri or sashimi so their texture is easy to appreciate.
Otoro is part of a tuna-fat hierarchy. Toro is the general term for fatty tuna; chutoro is moderately fatty, while otoro is generally the richest and fattiest grade. Akami, by contrast, is the lean red meat from the tuna’s central body, and maguro is a broader Japanese term for tuna rather than the name of one specific belly cut.
Availability and quality vary by tuna species, cut, season, and restaurant. Menus may also use “otoro” somewhat loosely, so the label does not guarantee one uniform level of marbling or flavor.