James Stewart Johnston (7 February 1811 – 10 August 1896) was a Scottish-Australian businessman, newspaper owner and politician, a member of the Victorian Legislative Council November 1851 to December 1852 (then unicameral) and the Victorian Legislative Assembly, October 1859 to August 1864.
Johnston was the only son of James Johnston, of the Paper Mills, Mid Calder, West Lothian, and was born in Edinburgh. He studied for the medical profession at the university, but ultimately abandoned it, and went to the West Indies, where, after two years, his health broke down, and he returned to Scotland.
In 1838 Johnston went to Tasmania, where he received a Government appointment in the office of the Superintendent of Convicts. In 1840, Johnston left for Port Phillip (Victoria), and started an hotel in Melbourne, where he became a member of the City Council, and ultimately an alderman. He gave up hotel-keeping about 1846.
Johnston was elected one of the first representatives of the City of Melbourne in the Legislative Council, then the only chamber, John O'Shanassy and William Westgarth being his colleagues. About this time he went into partnership with Edward Wilson in a cattle station near Dandenong, Victoria but the venture did not pay, and the partnership was dissolved, Johnston persuading Wilson to take to literary pursuits. Subsequently the two purchased the Melbourne Argus in equal co-partnership. The new venture did not at first pay better than the cattle station, and in 1852 Johnston sold his share to James Gill, who resold it to Lauchlan Mackinnon, whose interests Johnston subsequently represented in the management of the Argus when Mackinnon went to Europe.