| Term Start: | 1911 |
| Term End: | 1921 |
| Predecessor: | A. B. Aylesworth |
| Successor: | William Lyon Mackenzie King |
| Birth Date: | November 19, 1877 |
| Birth Place: | King Township, Ontario, Canada |
| Profession: | conveyancer, real estate agent |
| Party: | Conservative, Unionist Party |
| Riding: | York North |
John Alexander Macdonald Armstrong (November 19, 1877 – February 2, 1926) was a Canadian politician, conveyancer and real estate agent. He was elected to the House of Commons of Canada in the 1911 election as a Member of the historical Conservative Party and re-elected in 1917 as a Unionist. He ran in the elections of 1908 and 1921 as a Conservative and lost both elections. Born in King Township, Ontario, Canada, prior to his federal political experience, he served on King Township council as reeve of the township in 1908.