Marshall Lewis Johnston AO (20 July 1923 – 31 October 2017) was an Australian public servant and diplomat. Johnston enlisted in the Australian Army in 1941, during World War II. In June 1980 Johnston was appointed an Officer of the Order of Australia in recognition of his public service as a diplomatic representative. Johnston retired from public service in 1984, his final post was as Australian Ambassador to Greece (1980–1984). He died in October 2017 at the age of 94.