Antinous was born around the year 110 CE in Bithynium, a small city in the Roman province of Bithynia on the southern shore of the Black Sea. The region was Greek-speaking but provincial, a land of forests and mountains far from the glittering cities of Italy. His family was undistinguished; no ancient source records his parents' names or his social rank. What is certain is that he possessed a beauty so remarkable that it would be celebrated in marble across three continents. In 123 CE, when the emperor Hadrian toured the eastern provinces, he came to Bithynium and met the boy, then perhaps twelve or thirteen years old. Hadrian was already famous for his love of Greek culture, his restless travels, and his appreciation of male beauty. He took Antinous into his entourage, and from that day until the end of the boy's short life, the two were rarely apart.

For seven years Antinous travelled at the emperor's side. They journeyed through Italy and Greece, where both were initiated into the Eleusinian Mysteries, the secret rites of Demeter that promised initiates a blessed afterlife. They visited Syria, Arabia, and Judaea. In Libya they hunted a man-eating lion that had been terrorising the local population; the poet Pancrates celebrated the hunt in verse, describing how Antinous sat his horse with a spear in hand while Hadrian struck the beast with a bronze spear. The lion charged, the dust rose like a wave, and Hadrian saved his beloved's life. The episode was commemorated on the Arch of Constantine in Rome and in poems that circulated through the imperial court.

In August of 130 CE the imperial party arrived in Egypt. Hadrian had been suffering from a mysterious illness for several years, and the journey may have been partly a search for a cure. They visited the sarcophagus of Alexander the Great in Alexandria, restored the tomb of Pompey the Great, and travelled up the Nile. At Heliopolis, Hadrian consulted a priest named Pachrates who prepared potions and incantations. They moved on to Hermopolis Magna to celebrate the Festival of Osiris, the Egyptian god who died and was reborn, whose myth of drowning and resurrection would soon become Antinous' own. On 22 October 130 CE, during the Festival of the Nile, Antinous drowned in the river. His body was found floating in the water. He was not yet twenty years old.

The circumstances of his death were never explained to anyone's satisfaction. Hadrian wrote publicly that it was an accident, perhaps caused by intoxication. But three ancient sources suggest darker possibilities. Cassius Dio, the Greek historian who wrote in the third century, states bluntly that Antinous was "offered in sacrifice" to prolong Hadrian's life. Aurelius Victor agrees, reporting that when magicians demanded a volunteer to die in the emperor's place, Antinous offered himself while everyone else refused. The Historia Augusta records "varying rumours": some claimed he devoted himself to death for Hadrian, while others hinted at something "which both his beauty and Hadrian's excessive sensuality indicate." Whether he slipped, jumped, or was pushed into the river, whether he gave his life willingly or had it taken from him, the result was the same: the emperor lost the person he loved most in the world, and the ancient world gained a new god.

Hadrian's grief was public and overwhelming. The Historia Augusta records that he "wept like a woman," a phrase that shocked Roman sensibilities, which demanded stoic composure from its rulers. Within days of the drowning, Hadrian did what no Roman emperor had done before: he deified a private individual without consulting the Senate, without ancestral precedent, and without waiting for the passage of time to sanctify the dead. He founded the city of Antinoopolis on the east bank of the Nile, near Hermopolis Magna, laying it out as a Greek polis with a Hippodamian street grid, a gymnasium, a circus, baths, and temples. He granted it the constitution of Naukratis and filled it with settlers from Greek cities and army veterans. He erected a triumphal arch on the Nile and possibly a great mausoleum for Antinous within the city walls.

The cult spread with extraordinary speed. In Egypt, Antinous was identified with Osiris, the god who had drowned in the Nile and been restored to life. He became Antinous-Osiris, a dying-and-reviving deity who promised salvation to his worshippers. The Antinous obelisk, covered in hieroglyphs, proclaimed that "each God and each Goddess gives to him the breath of life and he breathes in a new youthfulness." In Greece, the city of Mantinea in Arcadia - which claimed kinship with Bithynia through the legendary Arcadian colonists who had settled there - built a temple to Antinous that Pausanias described as the newest in the city. The Mantineans held annual mysteries and quadrennial games in his honour, and filled a room in their gymnasium with statues that depicted him as Dionysus, crowned with ivy and holding the god's attributes. At Eleusis, ephebic games were established in his name. At Delphi, a priest of Antinous was inscribed in the theatre of Dionysus. At Athens, his cult was celebrated alongside the old gods. In his native Bithynium, the city was renamed Claudiopolis and later honoured him with the Hadrianeia Antinoeia, sacred games that drew competitors from across the region. A temple was built above the city's stadium, its eight Corinthian columns depicted on coins minted under the emperor Elagabalus.

The empire was flooded with images. Cassius Dio writes that Hadrian covered the whole inhabited world with statues of Antinous. More than two thousand have been estimated to have existed, though only a fraction survives today. They show him in every guise: as Osiris with the pharaonic headdress and uraeus, as Dionysus with the ivy wreath, as Hermes with the caduceus, as Apollo with the lyre, as Silvanus the woodland god, and simply as himself, a beautiful youth with full lips, heavy-lidded eyes, and a downward gaze that seems to look past the viewer into some private sorrow. The most famous image, the tondo from Hadrian's Villa at Tibur, shows him beside the emperor in a hunting scene, alive and alert. After his death, the villa itself became a shrine. The Antinoeion, a sanctuary built there immediately after the drowning, was filled with busts and statues of the new god in Egyptian and Roman styles, surrounding a central courtyard where white, red, and black stone portraits watched over the visitor.

The cult endured for more than two centuries. It offered something rare in Roman religion: a god who had been human, who had died young, and who could understand the grief of mortals. Inscriptions ask Antinous to protect the dead and guide their souls to a new life. At Lanuvium in Italy, a burial association worshipped Diana and Antinous together, meeting six times a year to ensure proper funeral rites for its members. But the cult also had enemies. Pagan writers like the author of the Historia Augusta mocked the oracles that were said to come from Antinous, claiming Hadrian composed them himself. Christian writers were more savage. Origen condemned the worship of a mortal as a god. Jerome in the fifth century pointed to the temples of Antinous as proof of pagan folly. Athanasius, writing under Constantine, denounced the cult as emperor-worship by another name. In 391 CE, the emperor Theodosius I outlawed all pagan cults, and the worship of Antinous died with the rest. His temples were abandoned, his statues buried, his city of Antinoopolis gradually faded into the Egyptian desert.