| William Costello Kennedy | |
| Constituency Mp: | Essex North |
| Parliament: | Canadian |
| Predecessor: | Oliver James Wilcox |
| Successor: | Albert Frederick Healy |
| Term Start: | 1917 |
| Term End: | 1923 |
| Birth Date: | 27 August 1868 |
| Birth Place: | Ottawa, Ontario, Canada |
| Death Place: | Naples, Florida, United States |
| Cabinet: | Minister of Railways and Canals (1921-1923) |
| Party: | Liberal |
William Costello Kennedy, (August 27, 1868 - January 17, 1923) was a Canadian politician.
Born in Ottawa, Ontario, he was first elected to the House of Commons of Canada in the riding of Essex North in the 1917 federal election as a Laurier-Liberal. He was re-elected as a Liberal in 1921. From 1921 until his death, he was the Minister of Railways and Canals in the government of William Lyon Mackenzie King.