This chapter analyses John Tzetzes’ Theogony, a long poem in political verse that narrates genealogies of mythical gods and heroes following the example of Hesiod. The poem was dedicated to the sebastokratorissa Irene, a powerful patron of the Komnenian aristocracy, and is an important witness to the role of classical learning in twelfth-century Byzantium. The first part of the chapter examines the relation of Tzetzes’ poem to Hesiod’s Theogony, the Homeric epics and the Catalogue of Women, a fragmentary ancient work ascribed to Hesiod. It also provides a list of the main literary sources of the poem, which demonstrates Tzetzes’ dependence on other ancient poets. The second part analyses the narrative voice of Tzetzes, his linguistic style and the didactic character of the poem. The chapter concludes with an examination of the audience of the Theogony and its function as a didactic poem, which reflects patronage relationships in the Komnenian period. The chapter thus sheds light on Tzetzes’ attitude towards the ancient authors by situating the Theogony within his broad activity as a professional poet and commentator of ancient texts.