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 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.

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 RMS Titanic.