||This biographical article needs additional citations for verification. (August 2007)|
|The Right Honourable
|42nd Australian Defence Minister|
|Preceded by||Jim Killen|
|Succeeded by||Gordon Scholes|
|Member for Division of New England|
30 November 1963 – 31 August 1998
|23nd Speaker of the Australian House of Representatives|
4 March 1998 – 10 November 1998
|Preceded by||Bob Halverson|
|Succeeded by||Neil Andrew|
|Leader of the National Country Party/
National Party of Australia
17 January 1984 – 9 May 1989
|Preceded by||Doug Anthony|
|Succeeded by||Charles Blunt|
10 June 1929 |
Sydney, New South Wales
|Political party||National Party of Australia|
|Children||1 son, 1 daughter|
Sinclair was born in Sydney, the son of a suburban accountant. He was educated at Knox Grammar School and at the University of Sydney, where he graduated in arts and law. Later, he practised law in Sydney, but soon developed an interest in farming, and acquired a property near Tamworth, in the New England region of northern New South Wales. In 1956, he married Margaret Tarrant, with whom he had three children. After the early death of his wife, in 1970, he married again, to former Miss Australia 1961, Rosemary Fenton, with whom he has one son. His eldest daughter, Fiona, is married to the former Australian politician Peter King.
Political career 
Two years afterwards, Sinclair was promoted to the ministry, becoming Minister for Social Services in the Liberal-Country Party coalition government of Robert Menzies. In 1968, he became Minister for Shipping and Transport. He and Doug Anthony were seen as the most likely successors to the veteran Country Party leader John McEwen, but when McEwen retired in 1971, it was Anthony who was elected party Leader, while Sinclair was elected Deputy Leader, becoming at the same time Minister for Primary Industry.
After spending the three years of the Whitlam Labor government in opposition, Sinclair again became Minister for Primary Industry in 1975, in the Fraser government. He held this position until 1979, when he was forced to resign from the ministry after being charged with forgery. The charges arose from a dispute over his father's will, on which he was accused of having forged his father's signature. He was acquitted of these charges in August 1980, and then returned to the ministry as Minister for Special Trade Representations. After the 1980 elections he became Minister for Communications. In May 1982, he became Minister for Defence, a post he held until the defeat of the Fraser government at the 1983 election.
Party leader 
In January 1984 Anthony resigned the leadership of the National Country Party (as the Country Party had been renamed in 1975), and Sinclair succeeded him. Under his leadership the party was renamed the National Party of Australia (NPA), reflecting the need to broaden the party's base beyond its declining rural constituency. The party aggressively challenged the Liberals in urban seats, but had little success except sometimes in Queensland.
Sinclair tried to position the NPA as the party of social conservatism. During the 1984 election he created a controversy by blaming the appearance of AIDS on what he claimed was the Hawke Labor government's policy of "condoning" homosexuality. He also wanted to reduce the number of Asian people immigrating to Australia.  In August 1988, he said:
"What we are saying is that if there is any risk of an undue build-up of Asians as against others in the community, then you need to control it ... I certainly believe, that at the moment we need ... to reduce the number of Asians ... We don't want the divisions of South Africa, we don't want the divisions of London. We really don't want the colour divisions of the United States." 
Sinclair had a poor relationship with Liberal leader Andrew Peacock, and supported his more conservative rival, John Howard. When Howard became Liberal leader in 1985, the two formed a close partnership.
This alliance was disrupted by the determination of the extremely conservative Queensland branch of the NPA and its leader, Premier Joh Bjelke-Petersen, to seize the national political agenda. The 76-year-old Bjelke-Petersen launched a campaign to make himself Prime Minister at the 1987 election. As leader of the NPA's most powerful branch, he forced Sinclair to break off the coalition agreement and support his bid. The "Joh for Canberra" campaign was a complete failure. Due to numerous three-cornered contests and swing voters' alarm at the prospect of Bjelke-Petersen being kingmaker in a hung parliament, the NPA lost several seats, particularly in Queensland, and the Hawke government was elected to a third term.
Following the 1987 debacle, Sinclair and Howard both found their leaderships under pressure. In May 1989, there were simultaneous, co-ordinated leadership coups in both parties, with Peacock displacing Howard as Liberal leader and Charles Blunt replacing Sinclair. When Blunt lost his seat at the 1990 election, Sinclair made a determined attempt to regain the NPA leadership, but was defeated by Tim Fischer, and retired to the back-bench. He was thus the first NPA leader since the formation of the Coalition to have never served as Deputy Prime Minister of Australia. By this time he was the Father of the House of Representatives. He was also the last serving Australian politician to be a member of the Privy Council of the United Kingdom, entitling him to the prefix "The Right Honourable".
Aged nearly 70 and having had heart problems for some time, Sinclair announced his intention to retire from parliament at the 1998 election. In February 1998 Howard appointed Sinclair as Chairman of the Constitutional Convention which debated the possibility of Australia becoming a republic, a role in which he won praise from all sides. When the Speaker of the House, Bob Halverson, suddenly resigned in March, Sinclair was elected to replace him.
Sinclair liked serving as Speaker so much that he wanted to run for another term. However, the NPA had already chosen another candidate in New England and Sinclair had no choice but to retire, which he did at the October 1998 election.
- Sendziuk, Paul (2003). Learning to trust: Australian responses to AIDS. Sydney: UNSW Press. p. 58. ISBN 0-86840-718-6. Retrieved 5 October 2009.
- Bird Rose, Deborah (2005). Dislocating the Frontier: Essaying the Mystique of the Outback. Canberra: Australian National University E Press. p. 35. ISBN 1-920942-37-8. Retrieved 30 November 2007.
- Markus, Andrew (2001). Race: John Howard and the Remaking of Australia. Allen & Unwin. p. 89. ISBN 1-86448-866-2.
- It's an Honour: AC