| Honorific-Prefix: | The Hon. |
| William Gordon Ernst | |
| Constituency Mp: | Queens—Lunenburg |
| Parliament: | Canadian |
| Predecessor: | William Duff |
| Successor: | John James Kinley |
| Term Start: | 1926 |
| Term End: | 1935 |
| Birth Date: | 18 October 1897 |
| Birth Place: | Mahone Bay, Nova Scotia, Canada |
| Party: | Conservative |
| Cabinet: | Minister of Fisheries (1935) |
William Gordon Ernst, (October 18, 1897 - July 12, 1939) was a Canadian politician.
Born in Mahone Bay, Nova Scotia, he first ran for the House of Commons of Canada in the 1925 federal election in the Nova Scotia riding of Queens—Lunenburg. A Conservative, he was defeated but he was elected in the 1926 federal election. He was re-elected in 1930 and defeated in 1935. In 1935, he was the Minister of Fisheries.
He served as a captain in the 85th Canadian Infantry Battalion during World War I and was awarded the Military Cross and Bar.