Tuna are several species of ocean-dwelling fish in the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers and like most other fish species are cold-blooded. Unlike most ocean fish species, which have white flesh, the flesh of tuna is pink. This is because the tuna's blood has a higher oxygen carrying ability than other fish species. Some of the larger tuna species such as the bluefin tuna can raise their blood temperature above the water temperature with muscular activity. Though not really warm-blooded, this enables them to live in cooler waters and survive a wider range of circumstances.

Tuna is a popular seafood. Some varieties of tuna, such as the bluefin, are endangered because of overfishing, while others are part of well maintained fisheries, such as the bigeye or yellowfin

Tuna are a common target for big-game fishing, and are mostly caught on artificial lures