Dame Edith Louisa Sitwell DBE (7 September 1887 – 9 December 1964) was a British poet and critic and the eldest of the three literary Sitwells. She reacted badly to her eccentric, unloving parents and lived much of her life with her governess. She never married but became passionately attached to Russian painter Pavel Tchelitchew, and her home was always open to London's poetic circle, to whom she was generous and helpful.

Sitwell published poetry continuously from 1913, some of it abstract and set to music. With her dramatic style and exotic costumes, she was sometimes labelled a poseur, but her work was praised for its solid technique and painstaking craftsmanship. She was a recipient of the Benson Medal of the Royal Society of Literature.

Edith Louisa Sitwell was born in Scarborough, North Riding of Yorkshire, the oldest child and only daughter of Sir George Sitwell, 4th Baronet, of Renishaw Hall; he was an expert on genealogy and landscaping. Her mother was Lady Ida Emily Augusta (née Denison), a daughter of William Denison, 1st Earl of Londesborough and a granddaughter of Henry Somerset, 7th Duke of Beaufort through whom she was descended from the Plantagenets in the female line.

Sitwell had two younger brothers, Osbert (1892–1969) and Sacheverell (1897–1988), both distinguished authors, well-known literary figures in their own right, and long-term collaborators. She described her childhood as "extremely unhappy" and said her mother had "terrible rages" while she rarely saw her father. Her relationship with her parents was stormy at best, not least because her father made her undertake a "cure" for her supposed spinal deformation, involving locking her into an iron frame. She wrote in her autobiography that her parents had always been strangers to her.

Whilst in Scarborough the Sitwell family lived in Wood End, a marine villa bought by Lady Louisa Sitwell in 1879 to which she added a double height conservatory filled with tropical plants and birds which Edith mentioned in her autobiography. Although Edith's relationship with Scarborough was not always a happy one, references to the seaside environment often occur in her work, particularly Facade.

In 1914, 26-year-old Sitwell moved to a small, shabby flat in Pembridge Mansions, Bayswater, which she shared with Helen Rootham (1875–1938), her governess since 1903.

Sitwell never married, but seems to have fallen in love with a number of unavailable men over the course of her life. Around 1914, she developed a passion for the Chilean artist and boxer Álvaro de Guevara, whom her biographer Richard Greene describes as "thuggish". Violent, unstable and addicted to opium, Guevara eventually became involved with the poet and socialite Nancy Cunard, whom Sitwell subsequently "never lost an opportunity to speak ill of".

She met the poet Siegfried Sassoon in 1918 and the two became close friends. Sassoon, who was homosexual, cared deeply for Sitwell, but Greene asserts that she fell in love with him, becoming jealous of his lover Stephen Tennant in the late 1920s. Sassoon and Sitwell were often seen out in each other's company, leading Sassoon's friend and mentor, the critic Edmund Gosse, to suggest that they marry. According to Sassoon's biographer, Max Egremont, Sassoon quickly replied: "I don't think poets should marry one another." Throughout the 1920s and '30s, Sitwell relied on Sassoon for criticism of her work, both privately and publicly. In 1922, he wrote a glowing review of Façade in the Daily Herald entitled "Too Fantastic for Fat-Heads", in which he compared Sitwell to the artist Aubrey Beardsley and declared: "Aubrey Beardsley has triumphed over all the fat-heads of his day. Miss Sitwell will do the same." Writing to him in 1933, Sitwell told him: "you are the only person who has ever done anything at all for my poetry."