The Catholic Bishop of Elphin has been formally installed in the same role for the neighbouring diocese of Achonry.
The appointment of Kevin Doran marks a step towards the two dioceses becoming one administrative area, as part of a reorganisation process.
Bishop Doran was installed during a service at the Cathedral of the Annunciation and St Nathy in Ballaghaderreen.
In his homily, Bishop Doran said the joining of both dioceses would lead to a "new kind of relationship" with all sorts of possibilities for those practicing their faith in the area.
He said that as well as making sure the structures of the Catholic Church were appropriate for the 21st century, measures were needed to support faith formation and also to ensure the "social mission" of the church was rediscovered.
The 71-year-old has served as Bishop of Elphin since 2014.
He was appointed Apostolic Administrator of Achonry last year, before being named as Bishop of the diocese in February.
The mass was concelebrated by the Papal Nuncio, Archbishop Luis Mariano Montemayor, along with the Archbishop of Tuam Francis Duffy and Bishop of Galway and Clonfert Michael Duignan.