| Office: | Judge of the Supreme Court |
| Term Start: | 7 March 1939 |
| Term End: | 17 January 1940 |
| Office1: | Judge of the High Court |
| Term Start1: | 5 June 1924 |
| Term End1: | 7 March 1939 |
| Birth Date: | 18 January 1868 |
| Birth Place: | Magherafelt, County Londonderry, Ireland |
| Death Place: | Dublin, Ireland |
| Children: | Denis Johnston |
| Education: | Methodist College Belfast |
William John Johnston (18 January 1868 – 29 November 1940) was an Irish barrister and judge.[1]
Born on 18 January 1868 near Magherafelt in County Londonderry, he was the eldest son of the seven children of James Johnston and his wife, Sarah (née Davidson). He was educated at Methodist College Belfast, and Queen's College, Belfast. He also studied at King's Inns and Gray's Inn.[1] [2]
He stood as a Liberal Home Rule candidate for South Londonderry at the December 1910 general election but was defeated by the Liberal Unionist MP John Gordon.[1] He became a member of the Pembroke Urban Council in 1911. He was the editor of The New Irish Jurist from 1899 to 1905, and of The Irish Law Times from 1906 to 1911.[1]
He was appointed as County Court judge of Monaghan and Fermanagh in 1911, and of Monaghan and Louth in 1921.[1] He was a High Court judge from 1924 to 1939, and from 1939 to 1940 served as a judge of the Supreme Court.[3] He later became the Commissioner of Charitable Donations and Bequests.[3]
In 1894, he married Kathleen King; they had one child, Denis Johnston born in 1901.[1] William John Johnston died in Dublin on 29 November 1940, aged 72.