Webb was born in London, England, into 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 1929, he was created Baron Passfield, but continued as a government minister (Secretary of State for the Colonies) under Ramsay MacDonald. The Webbs were supporters of the Soviet Union until their deaths, their book, The Truth About Soviet Russia being published in 1942.