Sir Peter John Westmacott GCMG LVO (born 23 December 1950) is a senior British diplomat, who was British Ambassador to Turkey, then Ambassador to France (2007 to 2011) and finally Ambassador to the United States from January 2012 to January 2016, succeeding Sir Nigel Sheinwald, a posting announced by the Prime Minister's Office on 24 June 2011.

[1] Westmacott joined the Foreign and Commonwealth Office in 1972, and his first overseas posting was as Second Secretary at Tehran, Iran, in 1974.

In 1990, he was Deputy Private Secretary to the Prince of Wales, and in 1993 was sent to Washington to serve as a Counsellor.

Later postings included Director for the Americas in the Foreign and Commonwealth Office, and Deputy Under Secretary of State.

[4] His cousin, Captain Herbert Westmacott MC, was killed during a gunfight with the Provisional Irish Republican Army in Belfast in 1980.