Siegfried Loraine Sassoon (8 September 1886 – 1 September 1967) was an English war poet, writer, and soldier. Decorated for bravery on the Western Front, he became one of the leading poets of the First World War. His poetry both described the horrors of the trenches and satirized the patriotic pretensions of those who, in Sassoon's view, were responsible for a jingoism-fuelled war. Sassoon became a focal point for dissent within the armed forces when he made a lone protest against the continuation of the war with his "Soldier's Declaration" of July 1917, which resulted in his being sent to the Craiglockhart War Hospital. During this period he met and formed a friendship with Wilfred Owen, who was greatly influenced by him. Sassoon later won acclaim for his prose work, notably his three-volume, fictionalised autobiography, collectively known as the Sherston trilogy.
Siegfried Sassoon was born to a Jewish father and an Anglo-Catholic mother, and grew up in the neo-gothic mansion named Weirleigh (after its builder Harrison Weir) in Matfield, Kent. His father, Alfred Ezra Sassoon (1861–1895), son of Sassoon David Sassoon, was a member of the wealthy Baghdadi Jewish Sassoon merchant family. For marrying outside the Jewish faith, Alfred was disinherited. Siegfried's mother, Theresa, belonged to the Thornycroft family, sculptors responsible for many of the best-known statues in London—her brother was Sir Hamo Thornycroft.
There was no German ancestry in Sassoon's family; his mother named him Siegfried because of her love of Wagner's operas. His middle name, Loraine, was the surname of a clergyman she respected.
Siegfried was the second of three sons, the others being Michael and Hamo. When he was four years old his parents separated. During his father's weekly visits to the boys, Theresa locked herself in the drawing-room. In 1895 Alfred Sassoon died of tuberculosis.
Sassoon was educated at the New Beacon School, Sevenoaks, Kent; at Marlborough College, Wiltshire; and at Clare College, Cambridge, where from 1905 to 1907 he read history.