The Fabian Society is a British socialist organisation whose purpose is to advance the principles of social democracy and democratic socialism via gradualist and reformist effort in democracies, rather than by revolutionary overthrow. The Fabian Society was also historically related to radicalism, a left-wing liberal tradition.

Socialism in the United Kingdom is thought to stretch back to the 19th century from roots arising in the aftermath of the English Civil War. Notions of socialism in Great Britain have taken many different forms from the utopian philanthropism of Robert Owen through to the reformist electoral project enshrined in the birth of the Labour Party that was founded in 1900.