Ion was the son of Xuthus or Apollo by Creüsa. Popularly he has come to be regarded as the personification of the Ionians, hence his name. But Euripides in his play Ion makes Xuthus explain his name as deriving from ion, 'going', since he had been told by the oracle that the first man he met on leaving the temple, that is when 'going' from it, would be his son.

Xuthus thus met Ion, assuming that he must be an illegitimate son (and that he would therefore have to break the news tactfully to Creüsa, who had never borne any children).