约翰·亚历山大·麦克唐纳爵士，GCB，KCMG，PC，PC (Can)，QC（Sir John Alexander Macdonald，1815年1月11日－1891年6月6日），加拿大首位总理。其政治生涯长达四十多年，在加拿大联邦中，扮演着举足轻重的角色。麦克唐纳总共担任了长达十九年的总理，时至今日，只有威廉·莱昂·麦肯齐·金打破了此纪录。

麦克唐纳生于苏格兰，在儿时随家人移民上加拿大金斯顿（今东安大略省）。成年后，他随当地一位律师学习法律，但这位律师在他取得律师资格之前就逝世了。虽然没有正式取得律师资格，他还是开办了自己的律师楼。麦克唐纳随后卷入了数宗知名的诉讼中，使他在当地名噪一时，他也因此在1844年取得了议会席位。1857年，他当选为联合副总理（Joint Premier）。

Sir John Alexander Macdonald GCBKCMGPCPCQC (11 January 1815 – 6 June 1891) was a Canadian politician and Father of Confederation who was the first Prime Minister of Canada (1867–1873, 1878–1891). The dominant figure of Canadian Confederation, he had a political career which spanned almost half a century. He drank heavily, and in 1873 was voted out during the Pacific Scandal, in which his party took bribes from businessmen seeking the contract to build the Pacific Railway. Macdonald's greatest achievements were building and guiding a successful national government for the new Dominion, using patronage to forge a strong Conservative Party, promoting the protective tariff of the National Policy, and building the transcontinental Canadian Pacific Railway. Economic growth was slow during his years in office, as Canada verged on stagnation; many residents migrated to the fast-growing United States. He fought to block provincial efforts to take power back from Ottawa. His most controversial move was to approve the execution of Métis leader Louis Riel for treason in 1885; it permanently alienated the Francophones who saw themselves humiliated.