The creatives join the other global partners, including Dan Wieden, the chief executive officer, Dave Luhr, the chief operating officer, Susan Hoffman and John Jay, the executive creative directors, and Bill Davenport, the executive producer.
Davidson and Papworth are the first partners to be appointed from outside W&K's Portland base and the first appointments to the global board since 1996.
Wieden said: "If you want to be a partner at W&K, you've got to be some kind of saint and some kind of crazy. No-one exemplifies that more profoundly than Tony and Kim. They have raised the bar, broken rules, lifted hearts and shocked the world."
Since joining the agency in 2000, Davidson and Papworth have been responsible for a number of award-winning campaigns, most notably the Honda "power of dreams" spot, which netted two black D&AD Pencils and the Grand Prix at Cannes.