The Pacific bluefin tuna (Thunnus orientalis) is a predatory species of tuna found widely in the northern Pacific Ocean, but it is migratory and also recorded as a visitor to the south Pacific.

In the past it was often included in T. thynnus, the 'combined' species then known as the northern bluefin tuna (when treated as separate, T. thynnus is called the Atlantic bluefin tuna). It may reach as much as 3 m (9.8 ft) in length and 450 kg (990 lb) in weight.