Stephenson, who oversaw the pitch process for the roster, has left to take a career break after just under two years with the firm.
Phil Hickley, head of public affairs, will be covering the external comms and public affairs part of Stephenson's role for the time being.
Stephenson said: "After two busy and enjoyable years at AXA, I have decided to take a short career break and will be spending the next few months on a sabbatical.
"I’m proud of the work that I was able to complete in my time at AXA, both in the UK and globally, and I would like to thank my colleagues for their support during that time. I will be exploring a number of exciting new opportunities after I return from travelling."
PRWeek understands AXA is set to confirm the creation of the roster, which is estimated by one well-placed source to be potentially worth a seven-figure sum and is thought to be an attempt to increase the flexibility of its agency arrangements, by October.
It includes five lots: consumer, creative, public affairs, City & corporate, financial and B2B.
A number of incumbent agencies, which span AXA’s various divisions and include Smithfield, Eulogy and Cicero Group, are thought to have pitched.
Of Stephenson’s departure, an AXA spokesperson said: "Following an orderly handover and the conclusion of a number of successful projects, Richard Stephenson decided to leave AXA at the end of July. Richard achieved a great deal in his time with the company and has recently led the review of our agency roster."
On Friday AXA posted strong global first-half financial figures, with net profit jumping 22 per cent year-on year to €3bn.