Serpens ("the Serpent", Ὄφις) is a constellation of the northern hemisphere. It is one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations defined by the International Astronomical Union. It is unique among the modern constellations in being split into two non-contiguous parts, Serpens Caput (Serpent's Head) to the west and Serpens Cauda (Serpent's Tail) to the east. Between these two halves lies the constellation of Ophiuchus, the 'Snake-Holder'.

The constellation Ophiuchus (Ὀφιοῦχος) has has had its stars interpreted in a number of ways throughout the years, and the Hellenic-era interpretations are mostly lost to us. Hyginus is our primary source on this constellation, and he was a Roman man. Many men could be represented with the constellation, but for Serpens, only one really applies: the healer-God Asklēpiós.

Asklēpiós splits Serpens into two distinct halves, as he was known for killing a snake that was resurrected because a different snake had placed a certain herb on it before its temporary death.  Hyginus has the following to say about Serpens and the affairs of this uplifting into the sky in his 'Astronomica':

"Many astronomers have imagined that he is Aesculapius, whom Jupiter, for the sake of Apollo, put among the stars. For when Aesculapius was among men, he so fare excelled the rest in the art of medicine that it wasn’t enough for him to have healed men’s diseases unless he could also bring back the dead to life. He is said most recently, according to Eratosthenes to have restored to life Hippolytus who had been killed by the injustice of his stepmother and the ignorance of his father. Some have said that by his skill Glaucus, son of Minos, lived again. Because of this, as for a sin, Jove struck and burned his house with a thunderbolt, but because of his skill, and since Apollo was his father, put him among the constellations holding a snake.
Certain people have said that he holds the snake for the following reason. When he was commanded to restore Glaucus, and was confined in a secret prison, while meditating what he should do, staff in hand, a snake is said to have crept on to his staff. Distracted in mind, Aesculapius killed it, striking it again and again with his staff as it tried to flee. Later, it is said, another snake came there, bringing an herb in its mouth, and placed it on its head. When it had done this, both fled from the place. Where upon Aesculapius, using the same herb, brought Glaucus, too, back to life.
And so the snake is put in the guardianship of Aesculapius and among the stars as well. Following his example, his descendants passed the knowledge on to others, so that doctors make use of snakes." [II.14]

Serpens is depicted as either winding around Ophiuchus in the night sky or simply passing through him, although the precise reason for either of these is unknown. In some ancient atlases, the constellations Serpens and Ophiuchus were depicted as two separate constellations, although in most they were shown as a single constellation.

Serpens is visible at latitudes between +80° and −80°, and best visible at 21:00 (9 p.m.) during the month of July.