Alderson was previously the commercial strategy director and managing partner at Bartle Bogle Hegarty until July last year.
In the newly created role, she will lead the planning function for Unilever, with a core focus on Dove. For O&M UK, Alderson will work with the group leadership team, operating company chief executives and heads of planning on strategic capabilities.
Alderson said: "Unilever is the agency’s biggest client and I am relishing the opportunity to help take Dove, a brand that I have hitherto admired from afar, and the rest of the Unilever portfolio forward.
"At a group level, Ogilvy has a future-facing infrastructure in place. Now is the time to galvanise the potential of the group’s specialist planning talent into a powerful combined force. A big team that can make a big difference."