Shawcross was educated at St. Aubyns Preparatory School, Rottingdean, Eton College and University College, Oxford. He attended St. Martin's Art School to study sculpture after leaving Oxford. He worked as a journalist for The Sunday Times. He writes and lectures on issues of international policy, geopolitics, Southeast Asia and refugees for a number of publications, including Time, Newsweek, International Herald Tribune, The Spectator, The Washington Post and Rolling Stone. He has also written a number of books, including biographies of Rupert Murdoch and the Shah of Iran. His official biography of Queen Elizabeth, the Queen Mother was released in the UK on 17 September 2009 and in the United States on 20 October 2009.
Shawcross was Chairman of ARTICLE 19, the international centre on censorship, from 1986 to 1996. He was a Member of Council of the Disasters Emergency Committee from 1997 to 2002, and a board member of the International Crisis Group from 1995 to 2005.
He was a member of the UN High Commissioner for Refugees's Informal Advisory Group from 1995 to 2000. From 1997 to 2003 he was a member of the BBC World Service Advisory Council. In 2008 he became a Patron of the Wiener Library and in 2011 he joined the board of the Anglo-Israel Society and was appointed to the board of the Henry Jackson Society.
Private life and honours 
Shawcross's father was the politician, lawyer, Chief British Prosecutor at Nuremberg and life peer Hartley Shawcross, his mother Joan Winifred Mather, who died in a riding accident on the Sussex Downs in 1974. Shawcross married the writer and art critic Marina Warner in 1970. Their son, Conrad, is an artist of rising prominence. He married twice more; he and his third wife, Olga Polizzi, are based in London. His daughter Eleanor, daughter of his second wife, Michal Levin, is a member of the Council of Economic Advisers to George Osborne, having been appointed in 2008 prior to Osborne assuming office. She had previously worked on Boris Johnson's mayoral campaign, where she was responsible for composing large parts of his manifesto. Eleanor is also married to Simon Wolfson, Baron Wolfson, the chief executive of the clothing retailer Next and a Conservative life peer. He is the son of former Next chairman David Wolfson, Baron Wolfson of Sunningdale, also a Conservative life peer.
Shawcross has lifelong ties to Cornwall where he is a keen campaigner in the preservation and protection of local Conservation Areas. There his one man campaign succeeded in obtaining Grade II listing for St Mawes' historic, and endangered, sea wall.
- Dubcek: Dubcek and Czechoslovakia 1918–1968 (1970), a New York Times Book of the Year
- Crime and Compromise: Janos Kadar and the politics of Hungary since Revolution (1974)
- Sideshow: Kissinger, Nixon and the destruction of Cambodia (1979), nominated for a Pulitzer Prize
- The Quality of Mercy: Cambodia, Holocaust and Modern Conscience (1984), awarded the Freedom From Hunger Media Award
- The Shah's Last Ride: The fate of an ally (1988)
- Kowtow!: A Plea on Behalf of Hong Kong (1989)
- Murdoch: The making of a media empire (1992)
- Deliver us from Evil: Warlords, Peacekeepers and a World of Endless Conflict (2000)
- Queen and Country (2002)
- Allies (2004)
- Queen Elizabeth The Queen Mother: The Official Biography (2009)
- Justice and the Enemy: Nuremberg, 9/11, and the Trial of Khalid Sheikh Mohammed (2011)
- Counting One's Blessings: The Selected Letters of Queen Elizabeth the Queen Mother (2012)
- The London Gazette: . 31 December 2010.
- Personal website
- Shawcross on Terror, a review of Justice and the Enemy: From the Nuremberg Trials to Khalid Sheikh Muhammad, by William Shawcross, in Policy Review, February and March 2012
- Justice and the Enemy: Nuremberg, 9/11, and the Trial of Khalid Sheikh Mohammed, review, January 2012
- Can torture be morally right?, Daily Mail, February 2012