The call to repentance is central to the message of early Christianity. While this is undeniable, the precise meaning of the concept of repentance for early Christians has rarely been investigated to any great extent, beyond studies of the rise of penitential discipline. In this study, the rich variety of meanings and applications of the concept of repentance are examined, with a particular focus on the writings of several ascetic theologians of the fifth to seventh centuries: SS Mark the Monk, Barsanuphius and John of Gaza, and John Climacus. These theologians provide some of the most sustained and detailed elaborations of the concept of repentance in late antiquity. They predominantly see repentance as a positive, comprehensive idea that serves to frame the whole of Christian life, not simply one or more of its parts. While the modern dominant understanding of repentance as a moment of sorrowful regret over past misdeeds, or as equivalent to penitential discipline, is present to a degree, such definitions by no means exhaust the concept for them. The path of repentance is depicted as stretching from an initial about-face completed in baptism, through the living out of the baptismal gift by keeping the Gospel commandments, culminating in the idea of intercessory repentance for others, after the likeness of Christ's innocent suffering for the world. While this overarching role for repentance in Christian life is clearest in ascetic works, these are not explored in isolation, and attention is also paid to the concept of repentance in Scripture, the early church, apocalyptic texts, and canonical material. This not only permits the elaboration of the views of the ascetics in their larger context, but further allows for an overall re-assessment of the often misunderstood, if not overlooked, place of repentance in early Christian theology.