Sailfish, the common name for a genus of game fish found primarily in the Atlantic and Pacific oceans. The sailfish is a fast swimmer and a tenacious, vigorous fighter. It has a long, slender body; a swordlike beak formed by the bones of the upper jaw; and a large, spotted dorsal fin (the “sail” for which it is named). It is dark blue on top and white or silver on the underside. Although highly prized as a game fish, the sailfish is not considered a particularly good food fish.

The Atlantic sailfish, found off the coasts of North and South America, can grow to a length of 10 feet (3 m). Average weight is about 40 pounds (18 kg). In spring the Atlantic sailfish migrates northward to reach cooler waters and a better food supply.

The Pacific sailfish, found south of the California coast, can grow to a length of 11 feet (3.4 m). Average weight is about 100 pounds (45 kg).

Sailfish belong to the billfish family, Xiphiidae. In some classifications the Atlantic sailfish is Istiophorus albicans and the Pacific, I. greyi; in others, both are considered to belong to the same species, I. platypterus.