Sir Ronald Graeme Millar (12 November 1919 - 16 April 1998) was an English actor, scriptwriter, and dramatist.
After Charterhouse and studying at King's College, Cambridge, for a year, Millar joined the Royal Navy in 1940, during the Second World War. He established himself as a playwright after the war and, between 1948 and 1954, lived in Hollywood, where he wrote scripts for MGM. On his return to Britain, he successfully adapted several C. P. Snow novels – and, in 1967, William Clark's novel Number 10 – for the stage. He also wrote the book and lyrics for the musical Robert and Elizabeth. He acted as speechwriter for three British prime ministers, including Margaret Thatcher, for whom he wrote the famous line "The lady's not for turning."
Millar was the son of a professional actress, Dorothy Dacre-Hill. Prior to becoming a full-time dramatist and then a speechwriter, Millar acted in a number of West End productions during and after World War II, in the company of luminaries as Ivor Novello, Alastair Sim and John Gielgud. He also appeared in the 1943 war film We Dive at Dawn directed by Anthony Asquith. One of his most well-received productions was Abelard and Heloise featuring Keith Michell and Diana Rigg.