Bradbury, formerly the integrated creative director of Saatchi & Saatchi X, joins rmg in January, reporting to Trefor Thomas, the EMEA chief creative officer.
Thomas said: "Guy is a great creative talent. He is diligent, focused and experienced. I am delighted he is joining us."
During his four-year spell at Saatchi & Saatchi X, Bradbury, an art director, collected, among others, two bronzes at Cannes and a gold Clio for his work for St Mungo's.
Bradbury said: "This was too exciting an opportunity to miss. There is huge potential at rmg and, with the team it has in place and the clients already on board, it is an exciting place to be."
Rmg has also hired the art director David Day, from Innocence, and the copywriter Nigel Edginton-Vigus, from TBWA\GGT, as a creative team. The two men are teaming up for the first time.