He joins from Wieden & Kennedy Amsterdam, where he was creative director on the agency's flagship Nike account.
Following the appointment, Gerry Moira, the Euro RSCG London director of creativity will relinquish day-to-day control of the creative department and take the new role of creative chairman. Moira will remain lead creative on a number of the agency's accounts, including Peugeot, EDF Energy and global projects on Reckitt Benckiser.
Cadman, the London chief executive, said: "Mark has the rare combination of outstanding creative craft skills and a wonderfully curious and stimulating mind. He's ambitious for the creative product, he is passionate about approaching things differently and, based on his track record, he'll help us deliver new and exciting work for our clients.
Hunter added: "I have spent all of my career at independent creative agencies so this is a big shift for me. But I am very excited by the opportunity at Euro RSCG London right now. I believe it is an agency moving in the right direction and hiring the right people. Getting the chance to work alongside guys like Mark and Russ (Lidstone) is not something that comes along every day.
Hunter started his career at the Toronto-based agency Harrod & Mirlin. He joined Bartle Bogle Hegarty in 1999 and won a D&AD Black Pencil in 2001 for the Levi's "twist" commercial he created with his then partner Tony McTeer.
During his time on Nike in Amsterdam, Hunter oversaw the launch of the Nike dance category, the relaunch of Nike Air and led the development of Nike's 2006 World Cup campaign, "Joga Bonito".