O Antiphons

The O Antiphons (also known as the Great Advent Antiphons or Great Os) are antiphons used at Vespers during the Magnificat on the last seven days of Advent in Western Christian traditions. They likely date to sixth-century Italy, when Boethius refers to the text in The Consolation of Philosophy. They subsequently became one of the key musical features of the days leading up to Christmas.

In the English-speaking world they are best known in their amalgamated form as the hymn "O Come, O Come, Emmanuel".