Athlone native Bishop Michael Duignan will be installed as Bishop of Galway next Sunday.
The current Bishop of Clonfert will take up his new role following Mass of Installation at Galway Cathedral.
Bishop Duignan will be the principal celebrant and will also preach the homily.
Archbishop Jude Thaddeus Okolo, Papal Nuncio to Ireland and Bishop Brendan Kelly will be the principal concelebrants.
Since Bishop Duignan is already a bishop, he will be installed rather than ordained.
Pope Francis appointed Bishop Michael Duignan, Bishop of Clonfert, to minister simultaneously as Bishop of Galway, Kilmacduagh and Apostolic Administrator of Kilfenora in late February.
The two Dioceses concerned are to be pastorally administered by the one Bishop with the Diocese of Clonfert including parishes in Roscommon.