The Central Bank's financial regulator and deputy governor, Matthew Elderfield, is stepping down.
A statement from the Central Bank said he plans to return home to the UK to ''pursue other interests'' in six months time.
Mr Elderfield took up the Central Bank post in January 2010. He was previously the chief executive of the Bermuda Monetary Authority from June 2007.
He also spent eight years at the UK Financial Services Authority.
Today's statement said that Mr Elderfield has waived his €100,000 bonus entitlement at the end of his contract.
He will also step away with immediate effect from involvement in supervisory and other issues if and where a conflict could be perceived.
An announcement is expected next week regarding a new position which Mr Elderfield is expected to take up in Britain.
It is understood to be likely that he will move into the private sector.
During his time as regulator Elderfield introduced stiffer fines for financial irregularities and boosted staff numbers at the regulator, which he said was surprisingly poorly resourced when he arrived.
He also called for a re-evaluation of financial crime laws, saying delays in prosecuting those involved in the collapse of the banks were undermining public confidence.
Last month he announced binding deadlines for banks to address troubled mortgages, saying it would force them to write down the value of housing loans if measures proposed were deemed unsustainable.
''Energy, commitment and integrity''
"Matthew accepted the role of financial regulator at a key moment in the history of the State. With energy, commitment and integrity he has managed the necessary transformation in our approach to the stabilisation, regulation and supervision of financial institutions'', Central Bank Governor Patrick Honohan said.
Professor Honohan said that Mr Elderfield had contributed enormously to the organisational effectiveness of the Central Bank.
''Although it was always evident to me that we were very likely to have Matthew with us for only a few years, it is sad that this period is now drawing to a close. We will miss him greatly, though the institutional structures he has built and the work practices he has inculcated will endure as his lasting legacy,'' he added.
Mr Elderfield said it was a ''great privilege'' to be a public servant in Ireland in such challenging times.
''But after some six years away, it is time to return home to London. With the help of a fantastic team at the Central Bank, I feel we have built a strong regulator and set Ireland on a path to financial stability,'' he said in today's statement.
Commenting on Mr Elderfield's departure, Finance Minister Michael Noonan said that his skill, expertise and experience will be a loss to the Central Bank of Ireland.
''But he is leaving at a time when normality is returning to the financial system and the Central Bank is suitably prepared to deal with his departure in six months time,'' he added.
Mr Elderfield's news follows the departure of other Central Bank senior figures Peter Oakes and Jonathan McMahon in recent months.