It began in 2014 as an effort to tap into the ecumenical collaboration of IEC2012. The different traditions would read, pray and celebrate the Bible together over one week.
Religious service will mark the commencement of the Week of Prayer for Christian Unity.
Church leaders attend ecumenical carols with students from both communities in Armagh.
Fr Damian McNeice is first Roman Catholic to hold this position in Council's fifty year history.