She moves to the role from her position as managing director at the Starcom MediaVest Group (SMG)-owned full service media agency, Spark.
Kittridge has been with SMG for eight years and has been based in a number of markets within the group, including Hungary, Poland, Hong Kong, China and in the US, in New York and Chicago.
SMG has "committed to invest significantly in its London Hub leadership", according to the group, and Kittridge's appointment follows the recent series of recent hirings and promotions, including John Antoniades to head SMG's multinational clients, and Damien Evans to global trading director.
Kittridge will report to Iain Jacob, president of global innovation and executive director for the EMEA region at SMG, and will initially run the agency's RSA global business.
Jacob said: "Barbara has deep digital experience and performance marketing experience, alongside extensive brand knowledge. Her mix of markets, performance and FMCG is rare indeed, and I am really pleased that she has chosen our London operations as her next career move.
"We are continuing to build and deepen our multinational client capability and Barbara is a great addition to this."
Kittridge said: "Returning to the UK is a bit of a homecoming for me. I am looking forward to working alongside and contributing to the EMEA team, which has clearly created a digitally focused, future-centric performance marketing model."
The agency is currently refreshing its management line-up. Recent appointments have included former Aegis digital head Ian James to the role of chief digital officer across the EMEA region, and former Universal McCann chief Geraud Benoit as operations director on SMG's Procter & Gamble account.