William Johnston (1829 – 22 April 1894) was a Scottish-born Australian politician.
He was born at Montrose to stonemason David Mellison Johnston and Agnes Merrillees. He migrated to New South Wales around 1838 and became a general merchant at Clarence Town on the bank of the Williams River. On 18 October 1853 he married Mary Little, with whom he had one son. In 1877 he was elected to the New South Wales Legislative Assembly for The Williams. The Williams was abolished in 1880 and largely replaced by Durham. Johnston stood for Durham, but was defeated by Herbert Brown.
- Green, Antony. "Elections for the District of Williams". New South Wales Election Results 1856-2007. Parliament of New South Wales. Retrieved 11 November 2020.
- Green, Antony. "1880 Durham". New South Wales Election Results 1856-2007. Parliament of New South Wales. Retrieved 23 April 2020.
- "Mr William Johnston (1829-1894)". Former Members of the Parliament of New South Wales. Retrieved 23 June 2019.