John Anthony Hardinge Giffard, 3rd Earl of Halsbury FRS(4 June 1908 – 14 January 2000), was a British peer and scientist. Halsbury succeeded to the title in 1943. He was Managing Director of the National Research Development Corporation 1949–1959, after having been Director of Research of Decca Record Company 1947–1949, and previously worked for Lever Brothers, and Brown-Firth Research Laboratories. Subsequently he served on many public bodies, including chairing the Committee on Decimal Currency (1961–1963). He was Chancellor of Brunel University.
In 1986, he tabled a Private Member's Bill in the House of Lords entitled "An act to refrain local authorities from promoting homosexuality"; it failed, but led to the enactment of the similar Section 28.
He was President of the British Computer Society during 1969–70.
In addition, he was also a friend of J. R. R. Tolkien and was one of the few people to read The Silmarillion in Tolkien's lifetime in 1957.
His grandmother was the Edwardian couturiere Lady Duff-Gordon, otherwise known by her professional name Lucile, and who was a survivor of the RMS Titanic disaster.