Major developments in poetic genre happened in Late Antiquity: some genres such as biblical epic first occurred in that period, and the generic openness of other late antique poems seems to question the notion of genre as such. In this chapter I argue that the classical system of poetic genre imploded in Late Antiquity and transformed into a more flexible and open system in which classical understandings of genre coexisted with both generic innovations and a reduced importance of genre itself. After imploding, late antique poetic genre continued to use traditional genre markers such as appropriate subject matter, generic models, and metre, but it also introduced generic innovations in the form of generically unique works, genre mixing, and new genres while at the same time playing down the significance of genre as a category. This transformation of poetic genre took place in both halves of the Roman Empire, as evidence from Greek and Latin poetry will show. As a consequence, both Greek and Latin poets used genre more flexibly and relied less on it to communicate with their audiences.