The Bloomsbury Group was a group of associated British writers, intellectuals, philosophers and artists in the early 20th century. Among the people involved in the group were Virginia Woolf, John Maynard Keynes, E. M. Forster, Vanessa Bell, and Lytton Strachey. Their works and outlook deeply influenced literature, aesthetics, criticism, and economics, as well as modern attitudes towards feminism, pacifism, and sexuality.

Although popularly thought of as a formal group, it was a loose collective of friends and relatives closely associated with the University of Cambridge for the men and King's College London for the women, who at one point lived, worked or studied together near Bloomsbury, London. According to Ian Ousby, "although its members denied being a group in any formal sense, they were united by an abiding belief in the importance of the arts." The historian Raymond Williams disputed the existence of the group and the extent of its impact.

All male members of the Bloomsbury Group, except Duncan Grant, were educated at Cambridge (either at Trinity or King's College). Most of them, except Clive Bell and the Stephen brothers, were members of "the exclusive Cambridge society, the 'Apostles'". At Trinity in 1899 Lytton Strachey, Leonard Woolf, Saxon Sydney-Turner and Clive Bell became good friends with Thoby Stephen, and it was through Thoby and Adrian Stephen's sisters Vanessa and Virginia that the men met the women of Bloomsbury when they came down to London.

In 1905 Vanessa began the "Friday Club" and Thoby ran "Thursday Evenings", which became the basis for the Bloomsbury Group, which to some was really "Cambridge in London". Thoby's premature death in 1906 brought them more firmly together and they became what is now known as the "Old Bloomsbury" group who met in earnest beginning in 1912. In the 1920s and 1930s the group shifted when the original members died and the next generation had reached adulthood.

The Bloomsbury Group, mostly from upper middle-class professional families, formed part of "an intellectual aristocracy which could trace itself back to the Clapham Sect". It was an informal network of an influential group of artists, art critics, writers and an economist, many of whom lived in the West Central 1 district of London known as Bloomsbury. They were "spiritually" similar to the Clapham group who supported its members' careers: "The Bloomsberries promoted one another's work and careers just as the original Claphamites did, as well as the intervening generations of their grandparents and parents."

A historical feature of these friends and relations is that their close relationships all pre-dated their fame as writers, artists, and thinkers.

The group had ten core members:

In addition to these ten, Leonard Woolf, in the 1960s, listed as "Old Bloomsbury" Adrian and Karin Stephen, Saxon Sydney-Turner, and Molly MacCarthy, with Julian Bell, Quentin Bell and Angelica Bell, and David Garnett as "later additions". Except for Forster, who published three novels before the highly successful Howards End in 1910, the group were late developers.