William Astor, 4th Viscount Astor

William Waldorf Astor III, 4th Viscount Astor (born 27 December 1951) is an English businessman and politician who sits as a Conservative hereditary Lord Temporal in the House of Lords. He is a member of the Astor family known for its prominence in business, society, and politics in both the United States and the United Kingdom.

William Waldorf III is the son of William Astor, 3rd Viscount Astor (1907–1966), and Sarah Kathleen Elinor Norton (1920–2013). From his father's later marriages, he has three younger half-sisters: Emily (born 1956), Janet (born 1961), and Pauline (born 1964). From his mother's remarriage to Thomas Michael Baring, he has a younger half-brother named Edward Richard Philip Baring (born September 1962). He was educated at Eton College.

Astor was a Lord-in-waiting (a House of Lords whip) from 1990 to 1993. He was then made a Parliamentary Under Secretary of State at the Department of Social Security. In 1994, he moved to the Department of National Heritage where he served until leaving the government in 1995.

He was a member of the Founding Council of the Rothermere American Institute at the University of Oxford.

Viscount Astor is Chairman of Silvergate Media and director of Networkers Plc (since 2007) and trustee of Stanley Spencer Gallery in Cookham.

Astor was an early opponent of the HS2 high-speed rail project.

Astor married Annabel Lucy Veronica Jones (born 1948), daughter of Timothy Angus Jones and Patricia David Pandora Clifford on 14 January 1976. They have three children:

• Hon Flora Katherine Astor (born 7 June 1976)
• Hon William Waldorf "Will" Astor IV (born 18 January 1979)
• Hon James Jacob Astor (born 1981)

The heir to the viscountcy is his elder son, Will, who married model Lohralee Stutz, daughter of Serge Alain Stutz and Lerma Villas, at East Hendred, Oxfordshire on 5 September 2009. They have a son William Waldorf Astor V (born 4 May 2012) and a daughter Allegra Annabel Astor (born 14 August 2013).

His wife Annabel's stepfather was his uncle Michael Langhorne Astor.

Viscountess Astor was previously married to Sir Reginald Sheffield, 8th Baronet by whom she is the mother of Samantha Cameron, wife of former Prime Minister David Cameron.