Sir Gervais Squire Chittick Rentoul KC (1 August 1884 – 7 March 1946) was a British Conservative politician.
He was the eldest son of Judge James Alexander Rentoul, M.P. for East Down 1890–1902, and his wife Florence Isabella Young. James Rentoul was something of an eccentric and one contemporary newspaper reported of him that "no man, woman or child wished to see him return to East Down." The family claimed to be descended from King Henry VII.
He was born in Plumstead and educated at the City of London School, the Royal University of Ireland and Christ Church, Oxford, where he obtained first class honours in Jurisprudence and was President of the Oxford Union Society. While at Oxford he was active in the Oxford University Dramatic Society (OUDS). Among the stage roles he played was Angelo in Measure for Measure (1906) and Petruchio in The Taming of the Shrew (1907), a production including the professional actresses Lily Brayton as Katherine and her sister Agnes as Bianca. After leaving Oxford he acted with the Old Stagers along with fellow barrister and OUDS alumnus C.W.Mercer, who subsequently acted as his best man.
In 1912 he married Christian Muriel Smart (b. 1884); they had one daughter, Sylvia (b. 1916) who married Ferenc Gallo. In 1924 he was Master of the Guild of Freemen of the City of London.
He was elected Conservative Member of Parliament for Lowestoft in 1922. He was founding chairman of the 1922 Committee (1923–1932) and Parliamentary Private Secretary to the Attorney-General (1925–1929). He became a barrister and took silk in 1930, becoming Recorder of Sandwich. He was knighted in 1929 and retired from Parliament in 1934.
He was portrayed on television by Robin Sachs in the play The Root of all Evil (1981), a dramatisation of the Seddon murder case in 1912 in which Rentoul had appeared for the defence.