James W. Johnston (29 August 1792 – 21 November 1873) was a Canadian lawyer and politician.

Johnston was a descendant of Loyalists who fled the United States during the revolutionary war.

In 1843, he left the Legislative Council to run for the elected legislative assembly and became government leader because of the support of moderate members who opposed the "extremism" of Joseph Howe but were willing to make some concessions.

He lost power when responsible government was instituted in 1848 but continued as leader of what became the Conservative Party and served as Premier from 1857 to 1860 and again from 1863 to 1864 before being appointed to the bench.

Johnston was an early supporter of Canadian confederation, seeing it as a means of correcting the failings of responsible government.