The Atlantic sailfish (Istiophorus albicans) cuts a truly striking profile, taking its name from the large and distinctive dorsal fin which runs along the length of its body. When extended, the dorsal fin is taller than the width of the body, and, with its pronounced upper jaw that is modified into a long, circular bill, an elongate torso and a strongly forked tail fin, this fish is one of the most magnificent of all ocean creatures.

Body colouration changes depending on level of excitement, but normally the Atlantic sailfish is dark blue along the back and silvery blue/white with brown spots underneath. On each side are 20 rows of longitudinal stripes made up of many light blue dots. The fins are usually blackish-blue, and the base of the first and second anal fins are tipped silvery-white. The sail (first dorsal fin) is scattered with many small, round black dots.

There is debate amongst scientists over whether or not the Atlantic sailfish (Istiophorus albicans) and the Indo-Pacific sailfish (Istiophorus platypterus) are separate species. Because of this, the Atlantic sailfish is also sometimes referred to as Istiophorus platypterus. There is very little genetic evidence to separate Atlantic from Indo-Pacific populations, but it is commonly accepted that there are marked morphological differences between the two, with the Atlantic sailfish typically reaching far smaller sizes than its Indo-Pacific counterpart.