Stewart, who under company policy will also retire from the Sun Life board, will leave the company Nov. 30. He will be replaced Dec. 1 by Dean Connor, currently Sun Life's chief operating officer.
The two will work closely until the hand-off late this year, the company said.
"On behalf of the board of directors and the entire Sun Life organization, I wish to thank Don Stewart for his tireless dedication, leadership and integrity throughout his four decades in financial services, almost all of that time spent with Sun Life," board chairman Ronald Osborne said in a release.
Stewart, who turns 65 this year is a native of Scotland. He joined Sun Life's London branch in 1969 and emigrated to Montreal in 1972. After a brief break from the company, he returned in 1980 to lead its Canadian group retirement services division, followed by a series of other divisions. He was appointed CEO in 1998.
In 2009, Stewart was appointed Chairman of Canada's National Task Force on Financial Literacy.
He said he is "very pleased" that Connor is succeeding him.
"His proven leadership experience and knowledge of our diverse business operations make him the right choice to lead Sun Life going forward. I have great confidence in his abilities."
Connor has also been appointed to the Sun Life board.
He has held several executive positions since beginning to work for Sun Life in 2006. Prior to that he worked in the group pension and benefits business at Mercer Human Resource Consulting, two of Sun Life's key focuses.
Osborne said the company is delighted that the strength of its management team allows the board to choose a new leader from within.
"Dean's extensive experience and strategic vision will be of enormous benefit as the company continues to build on its strengths," he said.
Meanwhile, the board also announced the appointment of James Sutcliffe, as chairman effective Dec. 1. Sutcliffe is currently chairman of the company's risk review committee.
Sun Life Financial is a leading international financial services organization providing a diverse range of insurance and wealth accumulation products and services to individuals and corporate customers. It has some $469 billion in assets under management.
Shares of Sun Life were up 20 cents to $29.25 on the Toronto Stock Exchange.
