He replaces Kim Manley, who resigned as chief marketing officer following a financial probe (Marketing, 22 December).
Littlewood, who joins in May, will take the role of board-level chief commercial officer, assuming control of global marketing for the drinks firm's brand portfolio, which includes Courvoisier and Tia Maria.
The role's remit has been broadened since Manley left to include the company's global duty-free business and international customer management.
Littlewood, currently senior vice-president of corporate marketing at Mars USA, has in the past worked as Mars' marketing director of Europe and UK group marketing manager.
The Allied Domecq role is his first in the drinks sector.