Vanessa Bell (née Stephen; 30 May 1879 – 7 April 1961) was an English painter and interior designer, a member of the Bloomsbury Group and the sister of Virginia Woolf.

Vanessa Stephen was the elder daughter of the art critic and historian Sir Leslie Stephen (1832-1904) and the philanthropist Julia Prinsep Duckworth (1846-1895). The family included her sister Virginia, brothers Thoby (1880–1906) and Adrian (1883–1948), half-sister Laura (1870–1945) whose mother was Leslie's first wife, Harriett Thackeray, half-sister Stella Duckworth, and half-brothers George and Gerald Duckworth, who were Julia's children from her first marriage. Later in life, Virginia stated that, during their childhood, she and Vanessa had been sexually abused by George and Gerald.

The family lived at 22 Hyde Park Gate, London, and spent summers at Talland, the Cornwall house that would become the setting for Virginia's 1927 novel To the Lighthouse. In London, Vanessa was educated at home in languages, mathematics and history, and took drawing lessons from Ebenezer Cooke before attending Sir Arthur Cope's art school in 1896. In 1901, she studied painting at the Slade School of Fine Art.

After the death her father in 1904, Vanessa sold 22 Hyde Park Gate and moved to Gordon Square in Bloomsbury with her sister Virginia and brothers Thoby and Adrian. Thoby began inviting his Cambridge friends to 'at-homes' on Thursday evenings, where they discussed literary and artistic issues. These gatherings led to the formation of the Bloomsbury Group, which included Lytton Strachey, Clive Bell, John Maynard Keynes, E. M. Forster, Desmond MacCarthy, Leonard Woolf, Roger Fry, David Garnett, Arthur Waley and Duncan Grant.

Vanessa's daughter-in-law, Anne Olivier Bell, described her as "a woman of grave and distinguished beauty, with a low and beautiful speaking voice, characteristics which tended to mask her wit and humour and capacity for laughter."

In 1907, Vanessa married Clive Bell. They had two sons, Julian and Quentin. The couple had an open marriage, with both taking lovers throughout their lives. Bell had several affairs, including one with Mary Hutchinson and an intimate, though platonic, relationship with Virginia.

In 1911 Vanessa went on holiday to Turkey with her husband and Roger Fry. While there, she suffered a miscarriage, and a mental breakdown. Virginia went to Turkey to nurse her and while there, both women fell in love with Fry. Vanessa and Fry began a long relationship; the onset of this relationship is what made Virginia decide to marry Leonard Woolf. Upon returning to London, Vanessa, Clive, Duncan Grant, and David Garnett, who were lovers, left London and moved to Wissett Lodge in Harbury, Warwickshire, before settling at Charleston Farmhouse near Firle, East Sussex. Keynes was a frequent member of the household, until his marriage to Lydia Lopokova, whom Vanessa disliked. At Charleston, Vanessa began an intimate relationship with Grant, with whom she had a daughter, Angelica, in 1918. While Grant stayed with Bell for the rest of her life, Clive Bell raised Angelica as his own child; she was not told that Grant was her father until 1937.

In 1913, Vanessa, Fry and Grant established the Omega Workshops, a collective which produced avant-garde furniture, textiles, and household accessories. It was a cross-fertilization of fine and applied arts and included contributions from artists such as Henri Gaudier-Brzeska, Wyndham Lewis and Frederick Etchells. Although they received several commissions, they struggled through World War I and closed the business in 1919.