New Zealand Post chief executive Brian Roche's departure was announced by his chairman, Sir Michael Cullen. Mr Roche will leave the group in April next year.
Chorus chief executive Mark Ratcliffe is to leave the company about the middle of next year.
Both men have led their respective companies through eras of great change and upheaval. Mr Ratcliffe has dealt with deregulation of the telecommunications industry and the introduction of ultra-fast broadband and Mr Roche has been fighting to keep the postal group relevant despite falling letter volumes and the closure of some outlets and sorting facilities.
Mercury director Mike Allen will leave the board on November 3 after seven years.
Sir Michael said Mr Roche had led the NZ Post Group ``superbly'' through a period of great challenges and positioned the company well for the future.
Mr Roche joined NZ Post as chief executive in January 2010.
After nearly seven years as chief executive, he said it was time for someone new to take up the role.
As chief executive, Mr Roche had overseen major achievements, including the introduction of alternative day mail delivery, the integration of its courier and postal business and growth in Kiwibank, Sir Michael said.
Investments had been made in the future of the business, including the introduction of innovative electric delivery vehicles and in Kiwibank.
NZ Post reported last week operating earnings of $197 million for the year ended June, down from $209 million in the previous year.
Chorus chairman Patrick Strange thanked Mr Ratcliffe for providing a long notice period, giving the board time to search for his successor.
Mr Ratcliffe remained committed to his responsibilities as chief executive and retained the full backing of the board.
``I have no doubt he will continue to drive Chorus for the next year with the same passion and energy he always has.''
Before his appointment as chief executive of the new Chorus in 2011, Mr Ratcliffe was chief executive officer of Chorus as an operationally separate business unit with Telecom. He was also Telecom's executive lead for the ultra-fast broadband project.
Chorus yesterday reported an operating profit of $594 million for the year ending June, down from the $602 million reported in the previous corresponding period.
Mercury chairwoman Joan Withers said Dr Allen's expertise in geothermal development meant he played a key role in both the company's domestic and international geothermal programmes.
During his tenure, Mercury completed two major geothermal developments which contributed to geothermal growing to become New Zealand's second-largest electricity fuel source.
The company had no immediate plans for further geothermal development, Mrs Withers said.
