Hydra
Hydra is a Zodiacal constellation otherwise known as the Water Serpent (female). It is one of the 48 Greek constellations originally described by the 2nd century astronomer Claudius Ptolemy (Wikipedia). Hydra remains one of the 88 modern constellations defined by the International Astronomical Union (Wikipedia).
Hydra (abbrev. = Hya; genitive = Hydrae) covers 1303 square degrees or 3.16% of the celestial sphere making it the 1st largest constellation. It contains 238 stars brighter than apparent magnitude 6.5, the brightest star being Alphard.
For more information see the entries for Hydra at Wikipedia and U. Wisconsin. For a chart of Hydra, see Hya (IAU).