Singapore Post chairman Lim Ho Kee, who has helmed the company's board since its 2003 initial public offering, is stepping down on May 10.
Mr Lim, who made his intention known after the end of SingPost's financial year on March 31, will step down as a director at the annual general meeting to be held in July.
The board has unanimously agreed to appoint Professor Low Teck Seng, a member, as chairman from May 10.
Mr Lim, 71, said he is giving early notice to ensure a proper handing over of his responsibilities.
"Some of you would be aware that I have been planning to step down now for almost three years but had felt compelled to stay and guide management," Mr Lim said in a letter to the board.
He said family commitments demand more of his time.
"It has been a long and satisfying journey since our IPO in 2003. We can all be proud of what SingPost has achieved.
"Among postal companies, I believe we stand out as a successful model of transformation."
The board thanked Mr Lim for his service and "his foresight that the postal sector was on a burning platform", adding that he had impressed on everyone the urgency to transform in order to survive.
"Mr Lim is a visionary and has championed SingPost's transformation into the iconic institution it is today with its global footprint.
"He has led us with not just his great intellect and business acumen, but also with his heart. It is difficult to think of SingPost without Lim Ho Kee," the board said in a statement yesterday.
Mr Lim began his career in banking and has more than 35 years in both the public and private sectors.
His resignation comes as the company remains embroiled in a saga over concerns about its corporate governance standards.
It began last December, when the company admitted an "administrative oversight" for not properly disclosing director Keith Tay's interest in a 2014 acquisition.
In response to concerns raised by shareholders and market watchers, SingPost appointed a special auditor to scrutinise the conflict-of-interest issues surrounding the acquisition. It also commissioned a separate review to address any wider governance issues.
SingPost said on Thursday that the special audit is in its final stages, and the auditors are preparing their report.
The review of its corporate governance is expected to be completed before its AGM in July.
Separately, SingPost yesterday announced that it has terminated the joint venture agreement between its unit SingPost eCommerce and PT Trikomsel with effect from March 31.
Following the termination of the proposed joint venture, PT TSI, which has been a dormant company since its incorporation, will be dissolved.