Uncertainty is a fundamental part of the human condition. Experiences thwart expectations, and the world is in constant need of interpretation, evaluation and disambiguation. When writing about the past, historians can approach this uncertainty in different ways and either eliminate it from their history or enact it. This book examines the dynamics between historiography and uncertainty in the works of Livy and Velleius Paterculus. Combining close readings and theoretical reflection, it develops a distinct concept of temporal and hermeneutic uncertainty and builds on this concept to shed new light on the narrative composition of their histories. It has been argued that narrative is an essential part of human life and civilization. While engaging with recent approaches to the theory of narrative, Uncertainty in Livy and Velleius explores historiographical narrative as a mode of grappling with uncertainty.