| Honorific-Prefix: | The Hon. |
| John Ewen Sinclair | |
| Constituency Mp: | Queen's |
| Parliament: | Canadian |
| Term Start: | 1917 |
| Term End: | 1925 |
| Term Start2: | 1926 |
| Term End2: | 1930 |
| Office3: | Senator for Queen's, Prince Edward Island |
| Appointed3: | William Lyon Mackenzie King |
| Term Start3: | 1930 |
| Term End3: | 1949 |
| Birth Date: | 24 December 1879 |
| Birth Place: | Summerfield, Prince Edward Island |
| Party: | Liberal |
| Cabinet: | Minister Without Portfolio (1921-1925) |
John Ewen Sinclair, (December 24, 1879 - December 23, 1949) was a Canadian politician.
Born in Summerfield, Prince Edward Island, the son of Peter Sinclair, he was first elected to the House of Commons of Canada in the Prince Edward Island riding of Queen's in 1917 federal election. A Liberal, he was re-elected in 1921. He was defeated in 1925 but was re-elected in 1926. From 1921 to 1925, he was a Minister without Portfolio. In 1930, he was appointed to the Senate of Canada representing the senatorial division of Queen's, Prince Edward Island. He served until his death in 1949.