sailfish, common name for a marine game and food fish belonging to the family Istiophoridae and related to the swordfish and the marlin. It is named for its high, wide dorsal fin, colored deep blue with black spots. Like the marlin it has a pikelike upper jaw and small scales embedded in its skin. The average length is 6 ft (180 cm), though it may reach 10 ft (305 cm). The Atlantic sailfish, Istiophorus americanus, found north to Cape Cod in summer, averages 60 lb (27 kg) in weight, while the Pacific sailfish, I. orientalis, grows to 100 lb (45 kg). Sailfish are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Perciformes, family Istiophoridae.

Valued food and game fish in the genus Istiophorus (family Istiophoridae) of warm and temperate waters worldwide. It has a long, rounded spear extending from its snout but is distinguished from marlins and related species by its slimmer form, long pelvic fins, and especially its large, sail-like dorsal fin, which is bright blue and spotted. Deep blue above and silvery below, they grow to about 11 ft (3.4 m) long and 200 lbs (90 kg) or more. They feed mainly on other fishes. Its classification is uncertain, and one (I. platypterus) to several species may be recognized.

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