| Alexander Johnston | |
| Constituency Mp: | Cape Breton |
| Parliament: | Canadian |
| Predecessor: | Charles Tupper |
| Successor: | District was abolished in 1903 |
| Term Start: | 1900 |
| Term End: | 1904 |
| Constituency Mp2: | Cape Breton South |
| Parliament2: | Canadian |
| Predecessor2: | District was created in 1903 |
| Successor2: | James William Maddin |
| Term Start2: | 1904 |
| Term End2: | 1908 |
| Office3: | Member of the Nova Scotia House of Assembly for Cape Breton |
| Term Start3: | 1897 |
| Term End3: | 1900 |
| Birth Date: | 24 April 1867 |
| Birth Place: | Richmond County, Nova Scotia, Canada |
| Death Place: | Ottawa, Ontario, Canada |
| Party: | Liberal |
| Honorific Suffix: | CMG |
Alexander Johnston, CMG (April 24, 1867 - November 30, 1951) was a Canadian journalist, civil servant and politician.
Born in Richmond County, Nova Scotia, Johnston was educated at the Common Schools and St. Francis Xavier College, Antigonish, Nova Scotia. He was the editor and proprietor of the Sydney Daily Record. He was elected, in 1897, to the Nova Scotia House of Assembly but he resigned his seat in 1900 in order to contest the riding of Cape Breton for the House of Commons of Canada. A Liberal, he was successful and was re-elected in 1904. He was defeated in 1908. Johnston was Deputy Minister of Marine and Fisheries from 1910 to 1933. He led the Canadian delegation to London which participated in the development of international regulations for safety at sea following the sinking of . Johnston was made a Companion of the Order of St Michael and St George in 1935. He died in Ottawa at the age of 84.