William Arthur "Bill" Neilson AC (27 August 1925 – 9 November 1989) was Premier of Tasmania from 1975 to 1977.
Born in Hobart, Tasmania, and educated at Ogilvie High School, Neilson became a postman. He married Jill Benjamin, daughter of Phyllis Benjamin, in Melbourne in 1948. They had one son Andrew and three daughters, Christine, Carol and Robin.
Neilson was elected to the Tasmanian House of Assembly on 23 November 1946 at the age of 21, representing the Australian Labor Party (ALP). For many years he was not only the youngest MHA in Tasmania, but also the youngest person to be elected to any Australian parliament.
He held various cabinet offices, including those of Minister for Tourism and Attorney-General. He was Minister for Education for over ten years from 1958 to 1969, and again from 1972 to 1974. He was made Attorney-General again on 12 April 1974, and five days later was also made Deputy Premier, Police Minister and Environment Minister. When the Premier Eric Reece was required to retire due to his age, Neilson was elected Tasmanian Leader of the ALP and Premier of Tasmania, on 31 March 1975. He resigned as Premier, and from Parliament, on 1 December 1977.
After his term as premier, Neilson accepted the position as Agent-General for Tasmania in London. In the 1980s, he wrote as a theatre critic for The Mercury newspaper in Hobart.
He died in November 1989, aged 64.