In the past century, scholars have observed a veritable full cast of characters from Roman comedy in the poetry of Catullus. Despite this growing recognition of comedy's allusive presence in Catullus' work, there has never been an extended analysis of how he engaged with this foundational Roman genre. This book sketches a more coherent picture of Catullus' use of Roman comedy and shows that individual points of contact with the theatre in his corpus are part of a larger, more sustained poetic program than has been recognized. Roman comedy, it argues, offered Catullus a common cultural vocabulary, drawn from the public stage and shared with his audience, with which to explore and convey private ideas about love, friendship, and social rivalry. It also demonstrates that Roman comedy continued to present writers after the second century BCE with a meaningful source of social, cultural, and artistic value.