Keith Sinjohn Joseph, Baron Joseph,, known as Sir Keith Joseph, 2nd Baronet, for most of his political life, was a British politician, intellectual and barrister. A member of the Conservative Party, he served as a minister under four prime ministers: Harold Macmillan, Sir Alec Douglas-Home, Edward Heath and Margaret Thatcher. He was a key influence in the creation of what came to be known as "Thatcherism".