William Francis Sheahan (Billy Sheahan) QC (3 September 1895* – 27 December 1975) was an Australian politician, elected as a member of the New South Wales Legislative Assembly. *He signed a Statutory Declaration in 1919 to declare that he had enlisted in the AIF on 20 March 1916 'aged 21 when I was only 20 years of age'. He declared that his correct date of birth was 3 September 1894; however his actual birth wasn't registered after 1 September 1895.
Born in Tumut, New South Wales, the son of the publicans of the hotel at Jugiong, Sheahan attended schools in Tumut and Goulburn.
Sheahan gained work as a clerk in the Crown Law Department in 1914 before enlisting in the Australian Imperial Force in 1916, serving in France and Flanders. Following World War I, Sheahan returned to the Crown Law Department, working there until 1930, when he received a Bachelor of Laws at the University of Sydney and established a large criminal law practice.
Elected the Australian Labor Party member for the New South Wales Electoral district of Yass in 1941, Sheahan served in parliament until 1973 (from 1950 as the member for Burrinjuck), holding the portfolios of Attorney-General of New South Wales, Minister for Transport and Minister for Health between 1950 and 1965. His son Terry Sheahan succeeded him as Member for Burrinjuck.