He will replace John Sandom, who will become chairman at 1HQ, the parent company of Distillery, Vibrandt and Vibrandt Form.
Artus said he was eternally grateful for his experience at Fitch, however the opportunity to join 1HQ was too good to miss.
He plans to build 1HQ into a company that is more aligned with today's needs.
Artus said: "While some of the bigger, public-quoted agencies will be trimming costs and overheads, we will be in a position to focus our efforts on strengthening and growing nimble teams and finding the very best talent to compliment what we have.
"We plan to come out of this recession in a strong position.
"Being able to focus on this and to ensure we continue to deliver the very best 'brand growth' solutions for our clients is our immediate goal."
Sandom said: "We both believe in the strategic, innovative and creative 'cocktail' offered by the 1HQ group of brands.
"Under Mark's leadership I believe we are well placed to seize opportunities and develop as a global brand agency."