Which is the biggest constellation?
Hydra (the serpent or water snake) is the largest of the 88 modern constellations we use in astronomy. It measures 1303 square degrees in total, and is over 100 degrees long.
Hydra is a southern hemisphere constellation. It has been known for millennia and was included in the 48 constellations listed by the famous astronomer Ptolemy in the 2nd century.
A depiction of Hydra, the biggest constellation, from 1825.