In Christian theology and political philosophy, five partially overlapping areas of meaning are treated in terms of reconciliation. (1) Dogmatic theology often operates with an umbrella concept covering the entire work of Christ. (2) Philosophical theology employs a concept of atonement/reconciliation that attempts to explain the overall rationality of Christian faith. (3) Reconciliation procedures in peacebuilding work typically employ a pragmatic set of contextual measures. (4) The Roman Catholic sacrament of reconciliation provides an institutional forgiveness of personal sins. (5) The New Testament concept of reconciliation elucidates God’s justice and Christ’s work, and these theological realities bear comparison with the Graeco-Roman practices of mediation and peacebuilding. While the present article attempts to explain the historical roots of all these meanings, its theological focus is on (3), (4) and (5). Meanings (1) and (2) are treated in more detail in the entry on ‘Atonement’. The article proceeds from the Greek terms katallassein, katallagē and closely-related words (apokatallassein, diallassein). In Christianity, these words are normally translated into Latin with reconciliare, reconciliatio. The English words ‘reconcile’ and ‘reconciliation’ are understood as being related to these roots. This approach means that other overlapping concepts, such as ‘atonement’ and the German Versöhnung (reconciliation), are treated insofar as they express this Greek and Latin tradition. At the same time, the article pays attention to the recent popularity of reconciliation discourses in political science and peacebuilding, considering that they express an autonomous continuation of this tradition.