John James Clark (23 January 1838 – 25 June 1915) was an Australian architect, who began his career at the age of 14 in the office of the Colonial Architect's Office in Melbourne, immediately after his family migrated from Liverpool in 1852. Clark's 30 years in public service, followed by 33 in private practice, produced some of Australia's most notable public buildings, and at least one in New Zealand.[1] He is most famous as the designer of Melbourne's Old Treasury Building aged only 19.