The Conservative and Unionist Party, more commonly known as the Conservative Party is currently the second largest political party in the United Kingdom in terms of sitting Members of Parliament (MPs), the largest in terms of public membership, and the oldest political party in the United Kingdom. It is the most successful political party in British history in terms of election victories, and is considered by some to be the most successful political party in the world. The current leader is David Cameron, who as Her Majesty's Loyal Leader of the Opposition heads the Shadow Cabinet.

The Conservative Party is descended from the Tory Party of the late eighteenth and early nineteenth Centuries. Its members are still commonly referred to as Tories and the party is still often referred to as the Tory Party. Although the Conservative Party was in government for two-thirds of the twentieth century, it has been in opposition in Parliament since losing the 1997 election to the Labour Party under Tony Blair and currently, Gordon Brown.