Johnston, William , (1829–1902), politician, was born at Downpatrick, Co. Down, 22 February 1829, the eldest of seven children of John Brett Johnston (d. 1853), a landowner, and Thomasina Ann Brunette Johnston (née Scott). He attended the Diocesan School at Downpatrick and then entered TCD, where he graduated BA in 1852. In the following year, after his father's death, he inherited the family's small estate, mainly at Ballykilbeg outside Downpatrick. There were significant debts attached to the estate, however, and throughout his life he would be bothered with financial worries. In 1848 he joined the Orange Order, and in 1855 established a newspaper, the Downshire Protestant, which ran for seven years. In 1857 he unsuccessfully contested a parliamentary by-election at Downpatrick as a conservative.
In the mid 1860s he took a leading role in Orange protest at the Party Processions Act of 1850 which banned such processions including Orange parades. On 12 July 1867 he headed an Orange parade from Newtownards to Bangor for which he was arrested and sentenced to two months imprisonment. He emerged a popular Orange hero and was elected in November 1868 as a conservative MP for Belfast against official conservative candidates. In parliament he spoke out against the Party Processions Act which was repealed finally in June 1872. He also supported the ballot act and land reform. At the 1874 general election he retained his Belfast seat as an official conservative candidate. In March 1878 he was appointed an inspector of fisheries (Ireland) and consequently vacated his parliamentary seat. In May 1885 he was removed from office because of a public speech. At the 1885 general election he was returned to parliament for South Belfast as an independent conservative member. Subsequently he was accepted as an official member and in 1886 became secretary of a new grouping of Irish unionist MPs at Westminster, which position he held until his death on 17 July 1902.
Johnston was the author of a number of novels, including Nightshade (1857). On 23 February 1853 he married Harriet Allen from Co. Kilkenny they had three sons and two daughters. He was buried in the graveyard of Rathmullen parish church in east Down. His papers are held at PRONI.