Dean joins from agency Euro RSCG, where he managed the Peugeot account. He previously worked on brands such as Heinz, Danone, Cadburys, Renault and Land Rover.
He replaces Eve Tyers, who leaves after nine years with Volkswagen Group.
Dean will be tasked with managing the development and direction of the Audi UK national media strategy, including developing "convention-challenging" campaigns to promote Audi's technological developments.
He will report to Audi UK head of marketing Dominic Chambers, who himself only joined the VW-owned marque in July after leaving Korean electronics brand LG at the end of 2010.
Chambers said: "Our ever expanding range and the new developments that arrive to enhance it seemingly on an almost weekly basis will undoubtedly present formidable communication challenges, but I am confident that Kristian will rise to them admirably."
Separately, Audi has announced the appointment of Martin Sander as its new UK director. Sander will join in January from his current role as chief executive of Audi Canada. He replaces Jeremy Hicks, who left to become managing director of Tata Motors Jaguar Land Rover.