Aviva chief financial officer (CFO) Pat Regan is to leave the company after three years to take up a post in Australia.
Regan, who joined the group in February 2010, will step down in June to become chief financial officer at Australian insurer QBE.
Aviva said it has begun the search for a new CFO, and committed to making a "first class" appointment.
"Pat has been a tremendous support in assisting me with Aviva's financial transformation," said Aviva CEO Mark Wilson.
"I am supportive of his decision, and he leaves with my best wishes and those of Aviva's board."
Two global vehicles
'Further plug advice gap'
Must appoint separate CEOs and boards
Advisers do come out well
Will report to Mark Till