Thatcherism is a form of British conservative ideology named after Conservative Party leader Margaret Thatcher that relates to not just her political platform and particular policies but also her personal character and style of management while in office. Proponents of Thatcherism are referred to as Thatcherites. The term has been used to describe the principles of the British government under Thatcher from the 1979 general election to her resignation in 1990, but it also receives use in describing administrative efforts continuing into the Conservative governments under John Major and David Cameron throughout the 1990s and 2010s. In international terms, Thatcherites have been described as a part of the general socio-economic movement known as neoliberalism, with different countries besides the United Kingdom sharing similar policies around expansionary capitalism.

Conservatism in the United Kingdom is related to its counterparts in other Western nations, but has a distinct tradition and has encompassed a wide range of theories over the decades of conservatism. The Conservative Party, which forms the mainstream right-wing party in Britain, has developed many different internal factions and ideologies.