Which constellation represents a southern fish?

The constellation that represents a southern fish is Piscis Austrinus.

Piscis Austrinus is Latin for “the Southern Fish,” a name that distinguishes it from Pisces, the zodiac constellation representing two fish. It occupies the southern celestial hemisphere and is traditionally shown drinking or swallowing the water poured by Aquarius, the Water-Bearer.

The constellation was one of the 48 listed by Ptolemy in the 2nd century and remains one of the 88 modern constellations. Its brightest star is Fomalhaut, a first-magnitude star that represents the fish’s mouth. Fomalhaut is also notable for its surrounding circumstellar debris disk.

Piscis Austrinus has several ancient mythological associations. Greek traditions describe it as the Great Fish, sometimes credited with saving Derceto or the goddess Isis. Its stars also have roots in older Babylonian star lore. The most common mistake is choosing Pisces: Pisces means “the fishes” and depicts a pair, while Piscis Austrinus is the distinct southern fish.