The deputy governor of the Central Bank of Ireland is to leave his post in six months.
Matthew Elderfield, who took up his role following Ireland's banking meltdown and economic collapse, will have served just over three and a half years in the job.
The regulator, who was being paid more than 300,000 euro a year, has waived a 100,000 euro bonus entitlement due at the end of his contract.
"Matthew accepted the role of financial regulator at a key moment in the history of the state," said governor Patrick Honohan.
"With energy, commitment and integrity he has managed the necessary transformation in our approach to the stabilisation, regulation and supervision of financial institutions.
"He has 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."
Mr Elderfield plans to return to London to pursue other interests, the Central Bank said.
Finance Minister Michael Noonan said the outgoing regulator deserved credit for his work at a time of turmoil.
He said: "He took up this post at a period of great financial instability in Ireland and has played a key role in greatly enhancing the regulatory environment and bringing stability to the Irish financial system."