A self-portrait

Sidney James Webb (July 13, 1859–October 13, 1947) was a British socialist, economist and reformer, normally referred to in the same breath as his wife, Beatrice Webb. He was one of the early members of the Fabian Society in 1884, along with George Bernard Shaw (they joined three months after its inception). Together with Beatrice Webb, Annie Besant, Graham Wallas, Edward R. Pease, Hubert Bland and Sidney Olivier, Shaw and Webb turned the Fabian Society into the pre-eminent political-intellectual society in England in the Edwardian era and beyond.

Webb was born in London to a professional family. He studied law at the University of London in his spare time, while holding down an office job, and in 1895 helped to establish the London School of Economics, using a bequest left to the Fabian Society by a benefactor. He was appointed its Professor of Public Administration in 1912, a post which he held for fifteen years. In 1892, Webb had married Beatrice Potter, who shared his interests and beliefs. The money she brought with her had enabled him to give up his clerical job and concentrate on his other activities. Both were members of the Labour Party and took an active role in politics, Sidney becoming MP for Seaham in 1923. In 1902, he and his wife were active also in the creation of The Coefficients, a small and rather secretive 'think tank'. In 1929, he was created Baron Passfield, but continued as a government minister (serving as both Secretary of State for the Colonies and Secretary of State for Dominion Affairs) under Ramsay MacDonald. In 1930 ailing health resulted in his stepping down from the Dominions Office, but retaining the Colonial Office. The Webbs were supporters of the Soviet Union until their deaths, their book, The Truth About Soviet Russia being published in 1942.

Weeb co-authored a pivotal book on the History of Trade Unionism (1894) with wife Beatrice Webb.

|- style="text-align: center;" | width="30%" |Preceded by:
Leopold Stennett Amery | width="40%" style="text-align: center;" |Secretary of State for Dominion Affairs
1929–1930 | width="30%" |Succeeded by:
James Henry Thomas

|- style="text-align: center;" | width="30%" |Preceded by:
Leopold Stennett Amery | width="40%" style="text-align: center;" |Secretary of State for the Colonies
1930–1931 | width="30%" |Succeeded by:
James Henry Thomas