Allan "Jo" Johnston is an Australian advertising creative executive and copywriter who was successful as a jingle writer, particularly in the 1970s and 1980s. He was born in Adelaide, Australia. Together with his long-time business partner Alan Morris, he formed the Australian advertising agency Mojo which enjoyed much Australian and some international success in the 1980s and whose name survived until 2016 as Publicis Mojo, the Australian subsidiary of the French multinational advertising and communications company holding Publicis Groupe.