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.