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.

Socialism is an economic and political philosophy encompassing diverse economic and social systems characterised by social ownership of the means of production, as opposed to private ownership. It describes the economic, political, and social theories and movements associated with the implementation of such systems. Social ownership can take various forms, including public, community, collective, cooperative, or employee. Traditionally, socialism is on the left wing of the political spectrum. Types of socialism vary based on the role of markets and planning in resource allocation, and the structure of management in organizations.