This thesis illustrates the substantial presence of monsters in Roman culture, and particularly in Augustan poetry. Through close reading of the texts, it identifies how various figures with abnormal bodies were used to explore and contest concepts of the normal, the familiar and the human, both in mythological and non-mythological contexts. A discursive Introduction surveys recent critical theories about monsters from a range of different disciplines, including anthropology, gender studies, psychoanalysis and film studies, with particular reference to concepts of the grotesque and the formless. Chapter 1 argues that three different kinds of non-mythological monster- the prodigious birth, the commodified 'freak', and the ethnographic oddity- reveal underlying structures of, and developments within, Roman authors' understanding of the unfamiliar, and beliefs about the social and cosmological implications of bodily abnormality. Chapters 2 and 3 discuss Augustan poetic treatments of various female mythological monsters. Chapter 2 treats Scylla, Medusa and the Sirens as provoking varying representational strategies in terms of visuality. In Chapter 3, the Furies and the Harpies are read as psychological and corporeal versions of a single conceptual framework, which imbricated femininity, bestiality, disease and madness. In Chapter 4, the Centaurs and the Minotaur are treated as contrasting figures, despite their shared man-animal hybridity. The Centaurs embody a violent, 'proto-epic' form of behaviour, shared by other mythic figures such as Hercules, which is both intolerable and necessary. The Minotaur is a mute man-eater, but Augustan poets contest his inhumanity vicariously through related female characters, and the ambiguity of the labyrinth (both 'unicursal' and 'multicursal') reflects this conceptual lack of closure. Chapter 5 discusses human multi-part monsters - anti-Olympian beings, the 'manymouths topos', Argus, Cacus and Geryon- arguing firstly that they metapoetically figure relationships between 'true' epic and other poetry, and secondly that, in their military and agrarian roles, they portray the failure of monsters to achieve types of sociality appropriate to different genres. In conclusion, monsters are both an important part of the study of Roman culture, and an apt demonstration of the benefits of a methodologically adaptive approach.