After 10 years as chairman of the Public Service Commission (PSC) and close to 50 years in the public service, Mr Eddie Teo, 71, will retire on July 31.
His successor is Mr Lee Tzu Yang, 63, the PSC deputy chairman who was chairman of the Shell companies in Singapore.
The Prime Minister's Office, in announcing Mr Teo's retirement yesterday, said he played an instrumental role in shaping the ethos of integrity, service and excellence that anchors the public service.
Prime Minister Lee Hsien Loong thanked Mr Teo for his dedicated service and sterling contributions.
"Your able leadership of the commission has contributed to the Singapore public service's continued high international standing," PM Lee said in a letter to Mr Teo, who was conferred the Order of the Nila Utama First Class last year.
"You exemplify the best traditions of the public service and have done Singapore proud... The public service has benefited from your sharp analysis and insightful views, and your contributions have been singularly outstanding."
Mr Teo, describing his 48 years in the public service as "most fulfilling, meaningful and challenging", said in an e-mail to The Straits Times: "Not once did I ever think of doing anything else.
"I feel sad as I will miss the people without whose support and commitment I would not have been able to accomplish anything."
A President's Scholar, he began his career in 1970 in the Security and Intelligence Division (SID). In nine years, at age 31, he became its director, a post he held until 1994.
From 1982 to 1986, Mr Teo was also director of the Internal Security Department, making him the only person to head both Singapore's external and internal intelligence organisations at the same time, PM Lee noted in his letter.
Later, at the PSC, Mr Teo would champion greater diversity in the public service leadership.
After becoming PSC chairman on Aug 1, 2008, he brought on board new members from different backgrounds and professions, from academia to social work and law.
It was also in his time that scholarships were awarded to students from a wider range of schools, including polytechnics. And they were encouraged to venture beyond the traditional destinations for their studies, with some heading to countries such as Egypt, Israel and Thailand.
PM Lee said Mr Teo had taken an innovative approach in selecting top talent, interviewing students and making them offers even before their final exams.
"You applied your keen eye for people and deep understanding of human nature and dynamics, honed over many years in the intelligence services, to identify future leaders for Singapore," he said. "You recognised that in senior public service leaders, strong intellect and ability were essential, but good character and commitment to Singapore were fundamental."
On the posts that left the deepest impression on him, Mr Teo said: "The two jobs I most enjoyed in my career were my first and last, in SID and in PSC. The two jobs may seem very different, but at their core, both involved sizing up people."
Asked if he had any parting advice for public servants, he said: "I would like to urge those public servants remaining in the service to stay true to our values and continue to serve Singapore and Singaporeans to the best of their ability, impartially and without fear or favour."
Mr Lee Tzu Yang, a graduate of the London School of Economics, joined Shell in 1979, rose through the ranks and retired as chairman of Shell companies in Singapore in 2014.
He is also a member of the Council of Presidential Advisers.
Among other key appointments, Mr Lee, who was awarded the Meritorious Service Medal in 2014, chairs the board of The Esplanade Company, the Singapore University of Technology and Design and the Founders' Memorial Committee.