Aengus (Old Irish Oengus), also called Aengus Og, the Young, and the Mac Oc, Young Son, is an Irish god associated with youth, love and poetic inspiration, a son of the Dagda and the river-goddess Boann. His conception is bound up with a trick of time: the Dagda held the sun still so that the whole affair passed in what seemed a single day, and so the child was said to be conceived and born between day and day.
In the best-known tale, Aislinge Oenguso (The Dream of Aengus), he falls sick with love for a maiden, Caer, whom he has seen only in dreams; he learns that she lives in alternate years as a woman and as a swan, and by choosing her in swan-form and becoming a swan himself he wins her, the two circling the lake together as birds, an image that has made Aengus a figure of romantic longing in later Irish literature. His home is the great Neolithic passage-tomb of Brug na Boinne (Newgrange), which in the myth he obtains from his father by a clever turn of words.