McDonough, who currently operates as marketing and R&D director as well as Ireland general manager at Muller, is set to join Molson Coors in June.
He replaces former marketing director Simon Davies, who left the brewer after 13 years to set up a marketing services agency.
Interim marketing director David Preston will take up the role of director of commercial innovation, reporting to McDonough, who will join the Molson Coors UK board.
Prior to his five-year stint at Muller, McDonough's roles included marketing controller at Bacardi Martini and German pet care marketing director at Mars.
McDonough will take over responsibility for a number of brands, including Carling, Grolsch, Coors Light and Sol, as well as recently acquired beers Cobra and Singha.
Mark Hunter, Molson Coors chief executive, said: "Filling one of the highest profile marketing roles in the UK was never going to be easy, but after an extensive international search, we knew we had found the right person."