Sir Osbert Sitwell was born in London on 6 December 1892, the son of Sir George Sitwell. He was raised in Derbyshire and educated at Eton. He sat for the exam for entry to Sandhurst twice but failed both attempts but later during the First World War Sitwell served as an officer in the Grenadier Guards, in France for various periods from 1914 to 1917. His experiences left him with hatred of war.
Along with sister Edith and brother Sacheverell, Osbert Sitwell was a patron and pioneer of style, remembered chiefly for his five-volume autobiography, Left Hand, Right Hand! (1945-50, comprising Left Hand, Right Hand!; The Scarlet Tree; Great Morning; Laughter in the Next Room and Noble Essences). A late addition to his autobiography, Tales my Father Taught Me, followed in 1962. His autobiography is full of marvellous evocative pictures of an age and a culture that now seem almost entirely vanished, and are remarkable for the portrait of the eccentric, exasperating figure of his father, Sir George. His memoirs achieved tremendous success in both Britain and the US.
Sitwell was the author of poems, short stories, novels and memoirs. The majority of his poetry is light and satiric. Though his earlier poem The Winstonburg Line (1919), was markedly pacifist in tone. His short stories include Triple Fugue (1924); the novel Before the Bombardment (1926), a novel describing the shelling of Scarborough in 1914 and its effect on the lonely, genteel female society of the town; Collected Poems and Satires (1931) and Selected Poems (1943).
Upon his father's death in 1943, Sitwell became 5th baronet. Sir Osbert Sitwell, who never married, died in 1969 after succumbing to Parkinson’s Disease.