Serapis (Koinē Greek: Σέραπις, later form) or Sarapis (Σάραπις, earlier form, originally Demotic: wsjr-ḥp, Coptic: ⲟⲩⲥⲉⲣϩⲁⲡⲓ Userhapi "Osiris-Apis") is a Graeco-Egyptian deity. The cult of Serapis was introduced during the third century BC on the orders of Pharaoh Ptolemy I Soter of the Ptolemaic Kingdom as a means to unify the Greeks and Egyptians in his realm. A serapeum (Koinē Greek: Σεραπεῖον serapeion) was any temple or religious precinct devoted to Serapis. The cultus of Serapis was spread as a matter of deliberate policy by the Ptolemaic kings, who also built the immense Serapeum of Alexandria. Serapis continued to increase in popularity during the Roman Empire, often replacing Osiris as the consort of Isis in temples outside Egypt.
Serapis was depicted as Greek in appearance but with Egyptian trappings, and combined iconography from a great many cults, signifying both abundance and resurrection. Though Ptolemy I may have created the official cult of Serapis and endorsed him as a patron of the Ptolemaic dynasty and Alexandria, Serapis was a syncretistic deity derived from the worship of the Egyptian Osiris and Apis and also gained attributes from other deities, such as chthonic powers linked to the Greek Hades and Demeter, and benevolence linked to Dionysus.
There is evidence that the cult of Serapis existed before the Ptolemies came to power in Alexandria: a temple of Serapis in Egypt is mentioned in 323 BC by both Plutarch (Life of Alexander, 76) and Arrian (Anabasis, VII, 26, 2). The common assertion that Ptolemy "created" the deity is derived from sources which describe him erecting a statue of Serapis in Alexandria: this statue enriched the texture of the Serapis conception by portraying him in both Egyptian and Greek style.
The name of the deity is derived from the syncretic worship of Osiris and the bull Apis as a single deity under the Egyptian name wsjr-ḥp. This name was later written in Coptic as ⲟⲩⲥⲉⲣϩⲁⲡⲓ Userhapi. "Sarapis" was the most common form in Ancient Greek until Roman times, when "Serapis" became common.
The most renowned serapeum was in Alexandria. Under Ptolemy I Soter, efforts were made to integrate Egyptian religion with that of their Hellenic rulers. Ptolemy's policy was to find a deity that should win the reverence alike of both groups, despite the curses of the Egyptian priests against the gods of the previous foreign rulers (e.g. Set, who was lauded by the Hyksos). Alexander the Great had attempted to use Amun for this purpose, but he was more prominent in Upper Egypt, and not as popular in Lower Egypt, where the Greeks had stronger influence.
The Greeks had little respect for animal-headed figures, and so a Greek-style anthropomorphic statue was chosen as the idol, and proclaimed as the equivalent of the highly popular Apis. It was named Userhapi (i.e. "Osiris-Apis"), which became Greek Sarapis, and was said to be Osiris in full, rather than just his ka (life force).
The earliest mention of a Sarapis occurs in the disputed death scene of Alexander (323 BC). Here, Sarapis has a temple at Babylon, and is of such importance that he alone is named as being consulted on behalf of the dying king. The presence of Sarapis in Babylon would radically alter perceptions of the mythologies of this era: the unconnected Babylonian god Ea (Enki) was titled Šar Apsi, meaning "king of the Apsu" or "the watery deep", and perhaps he is the one meant in the diaries. His significance in the Hellenic psyche, due to its involvement in Alexander's death, may have also contributed to the choice of Osiris-Apis as the chief Ptolemaic god.
According to Plutarch, Ptolemy stole the cult statue from Sinope in Asia Minor, having been instructed in a dream by the "unknown god" to bring the statue to Alexandria, where the statue was pronounced to be Sarapis by two religious experts. One of the experts was of the Eumolpidae, the ancient family from whose members the hierophant of the Eleusinian Mysteries had been chosen since before history, and the other was the scholarly Egyptian priest Manetho, which gave weight to the judgement both for the Egyptians and the Greeks.
Plutarch may not be correct, however, as some Egyptologists allege that the "Sinope" in the tale is really the hill of Sinopeion, a name given to the site of the already existing Serapeum at Memphis. Also, according to Tacitus, Serapis (i.e., Apis explicitly identified as Osiris in full) had been the god of the village of Rhakotis before it expanded into the great capital of Alexandria.
The statue suitably depicted a figure resembling Hades or Pluto, both being kings of the Greek underworld, and was shown enthroned with the modius, a basket/grain-measure, on his head, since it was a Greek symbol for the land of the dead. He also held a sceptre in his hand indicating his rulership, with Cerberus, gatekeeper of the underworld, resting at his feet. The statue also had what appeared to be a serpent at its base, fitting the Egyptian symbol of rulership, the uraeus.
With his (i.e. Osiris's) wife Isis, and their son Horus (in the form of Harpocrates), Serapis won an important place in the Greek world. In his 2nd-century AD Description of Greece, Pausanias notes two Serapeia on the slopes of Acrocorinth, above the rebuilt Roman city of Corinth and one at Copae in Boeotia.
Serapis figured among the international deities whose cult was received and disseminated throughout the Roman Empire, with Anubis sometimes identified with Cerberus. At Rome, Serapis was worshiped in the Iseum Campense, the sanctuary of Isis built during the Second Triumvirate in the Campus Martius. The Roman cults of Isis and Serapis gained in popularity late in the 1st century when Vespasian experienced events he attributed to their miraculous agency while he was in Alexandria, where he stayed before returning to Rome as emperor in 70. From the Flavian Dynasty on, Serapis was one of the deities who might appear on imperial coinage with the reigning emperor.
The main cult at Alexandria survived until the late 4th century, when a Christian mob destroyed the Serapeum of Alexandria in 385. The Theodosian decree of 380 implicitly included the cult in its general proscription of religions other than approved forms of Nicene Christianity.