Piscis Austrinus is a constellation in the southern hemisphere. It was first listed by the Greek astronomer Ptolemy in the 2nd century. The constellation's name means "the southern fish" in Latin. It was previously known as Piscis Notius.
Piscis Austrinus used to include the stars that now belong to the constellations Grus
became separate constellations in the late 16th century, when the Dutch astronomer Petrus Plancius created and named them.
Piscis Austrinus is usually depicted as the Great Fish swallowing the water that is flowing from the jar held by Aquarius, the Water Bearer
. In Greek mythology, the two fish that represent the constellation Pisces
are said to be the offspring of the Great Fish. In ancient Egypt, the constellation is associated with the fish that saved goddess Isis' life. Isis, in turn, placed both the fish and its offspring in the sky. The origin of the constellation's name, however, is uncertain.
The constellation Piscis Austrinus occupies an area of 245 square degrees and contains three stars with known planets. It can be seen at latitudes between +55° and -90° and is best visible at 9 p.m. during the month of October.
The brightest star in Piscis Austrinus is 
Fomalhaut, alpha Piscis Austrini, a class A main sequence star that emits excess infrared radiation and has a debris disk in orbit. Fomalhaut is also the 18th brightest star in the night sky. Its name is derived from the Arabic phrase meaning "mouth of the whale." Formalhaut is one of the 16 stars in the Castor Moving Group, along with 
Castor in the constellation Gemini
Vega in Lyra
. It lies 25 light-years from Earth. It is particularly notable for being the first star system containing an extrasolar planet that has been imaged at visible wavelengths.
TW Piscis Austrini is a flare star that lies only a light-year away from 
Fomalhaut and also a member of the Castor Moving Group. The two stars may form a physical pair and be travelling companions, sharing common motion through space. TW Piscis Austrini, also known as Fomalhaut B, is a dwarf star approximately 24.9 light-years from the Sun.
beta Piscis Austrini is another binary and the only other named star in the constellation. Its traditional name in China is Tien Kang ("heavenly rope").
Piscis Austrinus does not have any notable deep sky objects, only a few faint galaxies.
Piscis Austrinus belongs to the Heavenly Waters family of constellations, along with Delphinus
Constellations directly bordering Piscis Austrinus are Capricornus