The Dionysiaca /ˌdaɪ.ə.nɪˈzaɪ.ə.kə/ (Ancient Greek: Διονυσιακά, Dionysiaká) is an ancient Greek epic poem and the principal work of Nonnus. It is an epic in 48 books, the longest surviving poem from Greco-Roman antiquity at 20,426 lines, composed in Homeric dialect and dactylic hexameters, the main subject of which is the life of Dionysus, his expedition to India, and his triumphant return to the west.