In Greek and Roman mythological poetry, Morpheus is a god associated with sleep and dreams. He appears only in Ovid's Metamorphoses, as a son of Somnus (Sleep, the Roman counterpart of Hypnos) who takes human form in dreams. From the Middle Ages the name came to stand more generally for the god of dreams or of sleep. The opiate morphine was later named from Morpheus.
Adapted from Wikipedia, "Morpheus" · CC BY-SA 4.0
I.Ovid's account
The only ancient literary mention of Morpheus by name is in Ovid's Metamorphoses, in the story of Ceyx and Alcyone. Juno sends the messenger Iris to the cave of Somnus; Somnus then dispatches Morpheus to appear to Alcyone in a dream in the likeness of her husband Ceyx and announce his death at sea.
Ovid makes Morpheus one of the thousand sons of Somnus. No other dream-shape, he says, is more skilled at representing the gait, features, and speech of men, or their clothing and accustomed words. Like other sleep deities in Ovid, Morpheus is winged.
II.Brothers among the Somnia
Ovid calls Morpheus and his brothers the Somnia ("dream shapes"), who appear in dreams mimicking many forms. He names two further sons of Sleep: Icelos ("Like"), called Phobetor ("Frightener") by humans, who takes the form of beast, bird, or serpent; and Phantasos ("Fantasy"), who assumes the deceptive shapes of earth, rocks, water, trees, and other lifeless things.
These three names are found nowhere earlier than Ovid and may be Ovidian inventions. Some modern commentators treat them as literary rather than traditional mythical figures, though others suggest a possible Hellenistic background for the division of dream forms.
III.Later reception
After antiquity the name Morpheus broadened in European tradition to denote the god of dreams or sleep in general, detached from Ovid's narrow role as the human-shaped dream messenger. The early nineteenth-century chemist Friedrich Sertürner derived the name of the alkaloid morphine from Morpheus, reflecting the drug's sleep-inducing properties.