Major John Granville Morrison, 1st Baron Margadale TD, DL (16 December 1906 – 25 May 1996), was a British landowner and Conservative Party politician. An MP from 1942 to 1965, he notably served as Chairman of the 1922 Committee between 1955 and 1964.
Morrison was the son of Hugh Morrison and Lady Mary Leveson-Gower, daughter of the Liberal statesman Granville Leveson-Gower, 2nd Earl Granville. James Morrison was his great-grandfather. The family seat is the Fonthill estate in southern Wiltshire. Morrison was educated at Eton College and Magdalene College, Cambridge and served in the Royal Wiltshire Yeomanry in the Second World War, until recalled in order to stand for election to Parliament.
Morrison was appointed High Sheriff of Wiltshire for 1938. In 1942 he was elected Member of Parliament for Salisbury, a seat he held until 1965, and served as Chairman of the 1922 Committee between 1955 and 1964. On 1 January 1965 he was raised to the peerage as Baron Margadale, of Islay in the County of Argyll, in recognition of his "political and public services". He was also Lord Lieutenant of Wiltshire between 1969 and 1981. In January 1983, he was appointed a Deputy Lieutenant for Wiltshire, together with Mary Salisbury.