Unum Group announced Wednesday that Jon S. Fossel, 69, is retiring as non-executive chairman of the board of directors. William J. Ryan has been named non-executive chairman of the board of directors, succeeding Fossel. The transition will take effect on Sept. 30, when Fossel marks five years of service as chairman.

Fossel joined the board in 2002 and has served as non-executive chairman since October 1, 2006. He will provide consulting services to the company after his retirement. Ryan, 67, joined the board in 2004 and is currently chair of the Governance committee and a member of the Finance committee. He retired in 2009 as chairman of TD Banknorth Inc. Previously, he was president, chief executive officer and a director of TD Banknorth Inc. Ryan is also currently a director of Wellpoint, Inc.

"Consistent with my belief that board chairs should rotate periodically, I had indicated to the board earlier this year that I did not intend to serve more than five years as chairman," said Fossel. "I have decided that this would also be a good time for me to step off the board. The company has achieved a remarkable turnaround, and I am confident it is well positioned for the future."