Euripides's Ion is, essentially, an origin story for the Ionian race in play form, meant to be performed for an audience of high- and low-born citizens. The Ionians are one of the four ancient Greek tribes (the others being the Dorians, the Aeolians, and the Achaeans). Ion is considered one of the classic Greek tragedies, and it employs many of the devices of early Greek storytelling, primarily the use of irony and what is now known as the "Greek Chorus."

The Greek Chorus is just what you would think: a group of people who most often stood to the side of the stage and served as narrators for the play—sometimes speaking and sometimes singing to convey important information to the audience. In this way it is quite unique.

For at least the last 500 years, with some notable exceptions, most drama has consisted solely of the dialogue and actions of the characters, which presents the obvious problem of communicating the characters' inner thoughts. The Greek Chorus solves that problem.

In Ion, the title character is introduced by the god Hermes as an orphan he found abandoned on a mountain. Hermes rescued the orphan and delivered him to a Priestess in the Temple of Apollo at Delphi to be raised.

Outside the temple one day, a teenaged Ion (although not called that name yet) meets Creusa and her handmaidens (who serve as the Greek Chorus). Creusa is there to ask the oracles (fortune-tellers of a sort) why she has not been able to conceive a child with her husband Xuthus, something she desperately wants. She disguises this fact from the boy.

Xuthus arrives at the temple and is told by the oracles that the first man he meets when leaving the temple will be his son. He meets the young man and as they walk, Xuthus becomes convinced that this is his son, and he gives him the name Ion, but they decide to keep this fact secret.

Creusa's handmaidens, however, cannot keep the secret from Creusa, who assumes, after some bad advice, that Ion is the product of her husband's infidelity. She decides to murder Ion, but he finds out and seeks revenge on her in the temple. The Priestess then explains to Creusa that Ion is, in fact, her son (with the god Apollo): the son she abandoned. The two are overjoyed at having found one another.

At the end of the play, the goddess Athena appears and foretells that Ion will one day rule and that the land and its people will be named in honor of him.

Another of the primary devices in Ion is the use of irony, which in this case refers to the fact that the Greek chorus and the audience know much more information than the characters, who act in ways that are seemingly contrary to their true intent.

For example, it seems clear in the text that Ion longs for a mother, who he unknowingly meets in the form of Creusa. Creusa longs for a son, but attempts to poison him when she believes the boy to be the product of her husband's infidelity. Ion attempts to then kill her, the mother that he has been yearning for. Xuthus obviously wants a son and decides that Ion is his, not knowing that he is, in fact, Creusa's son with Apollo.

All of this mistaken identity comes close to destroying all the characters, but the intervention of Athena ensures it won't happen. This demonstrates another important theme in Greek tragedy: the gods are constantly interfering in and guiding the lives of humans. One way to look at this is to realize that life was often turbulent and unpredictable in ancient societies, and they explain these circumstances the only way they know how: by blaming and or praising the gods.

Ion uses these devices remarkably well, establishing that certain emotions like sorrow, uncertainty, anger, and heartbreak are truly universal and apply to audiences equally well, even thousands of years after the play was conceived.