The Week of Prayer for Christian Unity is an international Christian ecumenical observance kept annually between January 18 and January 25. It is an octave, that is, an observance lasting eight days.
The Week of Prayer for Christian Unity began in 1908 as the Octave of Christian Unity, and focused on prayer for church unity. The dates of the week were proposed by Father Paul Wattson, cofounder of the Graymoor Franciscan Friars. He conceived of the week beginning on the Feast of the Confession of Peter, the Protestant variant of the ancient Feast of the Chair of Saint Peter, on January 18, and concluding with the Feast of the Conversion of Saint Paul on January 25.