Peter Frederick Egerton Elstob (22 December 1915 – 21 July 2002) was a British soldier, adventurer, novelist, military historian and entrepreneur.

In his writing, he is best known for his lightly-fictionalized novel Warriors For the Working Day (1960) and his military history of the Battle of the Bulge, Hitler's Last Offensive (1971).

He joined International PEN in 1962 and served first as general secretary and later as vice-president for seven years during the 1970s, rescuing the organisation from financial failure; he also secured the future of the Arts Theatre Club in London in 1946.

His father, Frederick, was a chartered accountant whose work drew him and his family first to Calcutta and then to the United States in the immediate aftermath of the war.

Following high school, Elstob began a series of escapades that showed his signature taste for adventure and unconventionality:Then, for no particular reason – except, perhaps, his life-long antagonism to authority – he ran away from home and signed on as a ship's bellboy.

His father tracked him down and persuaded him to go to the University of Michigan, but Elstob failed his freshman's year and got into trouble with the police.

He was eventually freed and sent to France due to the intervention of Medora Leigh-Smith, a young Labour Party official he had met in England; his experiences gave him the material for his first novel, The Spanish Prisoner (1939).

Elstob was convinced that his rejection by the RAF and his inability to rise above the rank of sergeant was due to his efforts in Spain and supposed communist sympathies.

[2] During the 1960s Elstob joined the English centre of International PEN, the worldwide association of writers, quickly gaining a place on the executive committee and becoming press officer to the organisation.

During the following years he became more involved in PEN, eventually becoming its secretary-general and then vice-president over a seven-year term, placing the organisation on a firm financial footing.

[2] The protagonist of Gail F. Borden's novel Easter Day 1941 appears to be loosely based on Elstob, and his experiences in the fighting in the Western Desert in early 1941.