Bishop Mike, who has held his current role since 2003, will mark the end of his time in the Diocese with a special service a Bristol Cathedral.
Educated at Ridley Hall, Cambridge, he has had an extensive church career.
He served as curate in churches in Addiscombe and Slough before becoming Rural Dean of Amersham and Archdeacon of Berkshire. Before taking his current position, he was the area Bishop of Buckingham for five years.
Bishop Mike said that he and his wife, Anthea had decided the timing for right for him to retire.
He said: "I have loved my time in this Diocese and there are many people I shall deeply miss. Working with colleagues, both lay and ordained has been a privilege and a gift.
"There will be many opportunities between now and 30 September to say more, but my overwhelming sense is a deep gratitude for the privilege of serving amongst you all. Please pray for Anthea and me as we prepare for this next phase of our lives."
Bishop Mike's final service will be at Bristol Cathedral on 23 September at 3.30pm.