Sir Reginald Edward Manningham-Buller, 1st Viscount Dilhorne, Bt, KC, PC (August 1, 1905-September 7, 1980) was, as the 1st Baron Dilhorne, Lord High Chancellor of Great Britain from 1962 to 1964.

He was the only son of Sir Mervyn Edward Manningham-Buller , 3rd Baronet and MP (1876-1956), grandson of Sir Edward Manningham-Buller, 1st Baronet, of Dilhorne Hall, Staffordshire, a junior member of the Yarde-Buller family headed by Baron Churston. His uncle's seat of Dilhorne Hall having passed to an heiress ineligible for the baronetcy, Sir Mervyn made his home in Northamptonshire. Although locals now pronounce it "Dill-horn", Manningham-Buller preferred the previous pronunciation of "Dill-urn".

Reginald Manningham-Buller, educated at Eton College and Magdalen College, Oxford, was called to the Bar in 1927 and elected to the House of Commons in 1943 for Daventry. He was briefly a junior minister in the Government of Winston Churchill before it lost power in the elections of 1945, and became a KC in 1947. In 1950, his seat became South Northamptonshire. When Churchill regained power in 1951 Manningham-Buller was knighted and became Solicitor-General; in 1954 he was sworn of the Privy Council and became Attorney-General. In 1956 he succeeded his father as 4th Baronet. In the late 1950s, Bernard Levin gave him the nickname Bullying-Manners in his Parliamentary sketch.

He continued as Attorney-General under Anthony Eden and Harold Macmillan until July 1962, when he was rather abruptly named Lord Chancellor and sent to the House of Lords to replace Lord Kilmuir. Retained after Macmillan's retirement in the cabinet of Alec Douglas-Home, when the Conservatives lost the election of 1964 he was made Viscount Dilhorne and Deputy Leader of the Conservatives in the Lords.

In 1969, very unusually for a hereditary peer, he was named a Lord of Appeal in Ordinary and continued in this capacity until his death.

He and his wife, Lady Mary Lilian Lindsay (1910-2004), daughter of the 27th Earl of Crawford, had a son, who succeeded him in the title, and three daughters, the second daughter, Eliza, being the Director-General of MI5 since 2002.