Aion was an ancient Greek god linked to time, the universe, and the zodiac. The time Aion represented was endless, limitless, repeating, and circular. In this view, the future was a return of the past, later called "aevum" (related to the Vedic Sanskrit term "Ṛtú"). Philosophically and in myths, especially in secret religious practices, Aion was seen as the symbol of eternal time—time that never changes or ends, reflecting the unchanging nature of existence itself.

This kind of time was different from the time represented by Chronos, which was measured in a straight line, moving from past to present to future.

Aion was a god of repeating cycles, such as the years and the zodiac. Later in ancient times, he became connected to secret religious traditions focused on life after death, like the mysteries of Cybele, the Dionysian mysteries, Orphic religion, and the Mithraic mysteries. In Latin, Aion’s concept was sometimes expressed as Aeternitas, Anna Perenna, or Saeculum. He was often shown with an earth or mother goddess, such as Tellus or Cybele, as seen on the Parabiago plate.

Iconography and symbolism

Aion is often seen as a young man who is mostly nude, standing inside a circle that represents the zodiac. This image symbolizes endless and repeating time. Examples of this representation can be found in two Roman mosaics from Sentinum (modern-day Sassoferrato) and Hippo Regius in Roman Africa, as well as on the Parabiago plate. However, because Aion represents time as a cycle, he may also be shown as an older man. In the Dionysiaca, the writer Nonnus connects Aion to the Horae and states that he:

The image of a snake winding around itself is linked to the idea of a hoop or wheel through the ouroboros, which is a ring formed when a snake holds its tail in its mouth. The 4th-century Latin scholar Servius explains that the picture of a snake biting its own tail represents the repeating pattern of the year.

In his 5th-century work on hieroglyphs, Horapollo further explains that a serpent hiding its tail under its body represents Aion, while the ouroboros, which shows the serpent eating its tail, represents the kosmos.

Identifications

Martianus Capella, a writer from the 5th century CE, connected Aion with Cronus (also called Saturnus in Latin). Because of the name "Cronus," Aion was often mixed up with Chronos, the Greek god of time. Similarly, the Greek god of the underworld, Plouton (also known as Pluto), was sometimes confused with Ploutos, the god of wealth. Martianus described Cronus-Aion as the partner of Rhea (called Ops in Latin), who was also linked to Physis, the Greek word for "nature."

Franz Cumont, a scholar, proposed a theory about the Mithraic creation story. He suggested that Aion represented Unlimited Time, sometimes shown as Saeculum, Cronus, or Saturn. According to Cumont, Aion emerged from the beginning of the universe, called Chaos, and then created Heaven and Earth. Modern researchers refer to this figure as the "leonto-cephaline" god, a winged, lion-headed man with a serpent wrapped around his body. He often holds a scepter, keys, or a thunderbolt. While the exact identity and meaning of this figure remain unclear, many of his symbols match those of Aion. In rare cases, statues of this figure show a human face instead of a lion’s head, making it look like Aion.

Some Christian and Neoplatonic writers connected Aion with Dionysus, the Greek god of wine and celebration. However, there are no records of Dionysus being called Aion before the time of Christianity. The ancient Greek playwright Euripides did describe Aion as the "son of Zeus."

The Suda, an ancient encyclopedia, linked Aion with Osiris and Adonis. This may be because Adonis was originally a god but later became a mortal after being believed to have died. In Ptolemaic Alexandria, a city in Egypt during the Ptolemaic period, the god Serapis was sometimes called Aion Plutonius. The name "Plutonius" connects this figure to Pluto, the Greek god of the underworld and the husband of Persephone. A Christian writer named Epiphanius recorded that in Alexandria, a festival celebrated Aion’s birth from Kore, the Virgin (Persephone), on January 6th. This date, which matches the Christian holiday of Epiphany, marked the end of New Year celebrations and symbolized the completion of the cycle of time that Aion represents.

In Alexandria, Aion may have been seen as a form of Osiris-Dionysus, a god who was reborn each year. His image often had crosses on his hands, knees, and forehead. A scholar named Quispel suggested that this figure might have developed by combining the Orphic god Phanes, who is also linked to a coiling serpent, with Mithraic religious beliefs in Alexandria. He believed this figure ensured the city’s lasting existence.

In Roman art, Aion was often shown as the same as Uranus or Caelus, ancient gods who represented the sky and the beginning of the universe.

Roman Empire

This blending of ideas made Aion a symbol that showed the lasting power of Roman rule. Emperors like Antoninus Pius made coins with the word "Aion" on them. Aion's female Roman version was called Aeternitas. Roman coins linked both Aion and Aeternitas to the phoenix, which represented rebirth and repeating cycles of renewal.

Aion was one of the virtues and spiritual figures discussed in late Hellenic times. These figures were seen as important in explaining the universe's structure. Aion's importance came from his ability to change and adapt. He helped bring together different ideas about time and gods during the Hellenistic period, when people were blending traditions and exploring ideas about a single god.