William Leonard Grayden (born 5 August 1920) is a former Australian politician. He was born in Perth, Western Australia. He was in the military with the 2/16th Infantry Battalion from 1940–1946.
In 1947, he was elected to the Western Australian Legislative Assembly as the Liberal member for Middle Swan, where he remained until 1949.
Along with George Pearce, Grayden is the earliest surviving MP, and one of only two living "Forty-Niner" Liberal MPs.