The Socialist Green Unity Coalition is an electoral alliance formed by leftist parties and political organisations in Great Britain prior to 2005 parliamentary election after the Respect Unity Coalition (which the SGUC constituent organisations regarded as little more than a vehicle for the Socialist Workers Party) rejected requests to discuss an electoral arrangement to avoid clashes in 2005. It was established in September 2004, named in November 2004 and publicly launched in February 2005. After the 2005 election the coalition continued to operate as a liaison and co-ordinating body but has not extended its remit much beyond electoral co-ordination.
The largest single component is the Socialist Party. Other participating organisations include the Alliance for Green Socialism (standing under their own name), Alliance for Workers Liberty and Socialist Unity Network (both standing as Socialist Unity) and the Democratic Socialist Alliance, whose candidates in 2005 were also members of the United Socialist Party. Many of these organisations were in the previous Socialist Alliance before it voted to support the established of the Respect Unity Coalition.
All the SGUC member organisations campaigned on a common platform including calls for an end to privatisation, for defence of the welfare state, an end to poverty and for full employment. The SGUC also gave greater priority than most of its individual members to the question of the environment and building a sustainable economic system - largely due to the influence of the Alliance for Green Socialism.