The Hon. Sir Gerald Alfred Thesiger MBE (born 25 December 1902, died 1981) was a judge of the High Court of England and Wales of the Queen's Bench Division between 1958 and 1978.
The son of Major-General George Handcock Thesiger and his wife Frances Fremantle, daughter of General Fitzroy William Fremantle, he was educated at Gresham's School, Holt, Magdalen College, Oxford (1922–1925), and the Inner Temple.
Thesiger's grandfather was Lt.-General the Hon. Charles Wemyss Thesiger, a younger son of a Lord Chancellor, Frederic Thesiger, 1st Baron Chelmsford.
The British general Frederic Thesiger, 2nd Baron Chelmsford, and the judge Alfred Henry Thesiger (one of the youngest Lords Justices of Appeal in history) were his great-uncles.
In 1926, he was admitted as a barrister. He was appointed Recorder of Rye in 1937.
During World War II, he was commissioned as a Major in the Office of the Judge Advocate General, and was appointed Recorder of Hastings in 1942. He entered local government in London, initially as a member of Fulham Borough Council from 1934–37 and then of Chelsea Borough Council from 1937-58. He was Mayor of Chelsea from 1944 to 1946. He took silk as a King's Counsel in 1948 and was appointed Recorder of Southend-on-Sea in 1952. He became a Bencher of the Inner Temple in 1956 and served as a High Court Judge of the Queen's Bench Division between 1958 and 1978.