The Church of England's longest-serving bishop, Dr Peter Forster, says he will retire later this year and move to Scotland.
Ill health prompted the retirement of the Bishop of Monmouth, Rt Rev Richard Pain on Tuesday.
Details of a farewell service for Bishop Richard will be revealed soon, the Church in Wales said.
Archbishop of Wales, John Davies commented: "Bishop Richard has been a faithful and much-loved priest to those he has served and a valued colleague to myself and the other bishops.
"I ask for your prayers for him and his wife Julie as they prepare for his retirement, and also for the Diocese as it embarks on an interregnum."
Sickness had forced Bishop Richard to take a leave of absence from his duties for several months.
Oversight of the diocese will now be the responsibility of Archbishop John (pictured below) until a successor is chosen.
Archbishop John added: "The extended absence of a key, senior colleague brings additional pressures to others, and I am grateful to the senior staff team and those others who have taken on additional tasks and responsibilities during this time.
"I would also like to thank parishioners for the patience and understanding they have shown."
After training at the Anglican theological college, St Michael's in Llandaff, Bishop Richard started his ministry as a curate in Caldicot 34 years ago.
He served as parish priest in Six Bells and Cwmtillery, Risca, Overmonnow and Monmouth, before becoming Archdeacon of Monmouth in 2008.
Richard became Bishop of Monmouth five years later.
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