In Greek mythology, Hymenaios (also Hymenaeus, Hymenaues, or Hymen; Ancient Greek: Ὑμέναιος) was a god of marriage ceremonies, inspiring feasts and song. A hymenaios is also a genre of Greek lyric poetry sung during the procession of the bride to the groom's house in which the god is addressed, in contrast to the Epithalamium, which was sung at the nuptial threshold.
Hymenaios was celebrated in the ancient marriage song of unknown origin Hymen o Hymenae, Hymen delivered by G. Valerius Catullus. Both the term hymn and hymen are derived from this celebration.
He is also mentioned in Virgil's Aeneid and in five plays by William Shakespeare: Hamlet, The Tempest,Much Ado about Nothing, Titus Andronicus, and As You Like It, where he joins the couples at the end —
Hymenaios also appears in the work of the 6th- to 7th-century Greek poet Sappho (translation: M.L. West, Greek Lyric Poetry, Oxford University Press):
He was the son of Bacchus (god of revelry) and Aphrodite (goddess of love); or, in some traditions, Apollo and one of the Muses.
Other stories give him a legendary origin. In one of the surviving fragments of the Catalogue of Women associated with Hesiod, it's told that Magnes "had a son of remarkable beauty, Hymenaeus. And when Apollo saw the boy, he was seized with love for him, and wouldn't leave the house of Magnes" 
Aristophanes' Peace ends with Trygaeus and the Chorus singing the wedding song, with the repeated phrase "Oh Hymen! Oh Hymenaeus!"
, a typical refrain for a wedding song.
Hymenaios disguised himself as a woman in order to join one of these processions, a religious rite at Eleusis where only women went. The assemblage was captured by pirates, Hymenaios included. He encouraged the women and plotted strategy with them, and together they killed their captors. He then agreed with the women to go back to Athens and win their freedom, if he were allowed to marry one of them. He thus succeeded in both the mission and the marriage, and his marriage was so happy that Athenians instituted festivals in his honour and came to be associated with marriage.