Sir Alvary Douglas Frederick Trench-Gascoigne GBE, KCMG (6 August 1893 – 18 April 1970) was a British diplomat.

He was the son of Colonel Frederic Richard Thomas Trench Gascoigne and Laura Gwendolen Douglas Galton.

His great-aunt Elizabeth Oliver Gascoigne was the wife of Frederick Mason Trench, 2nd Baron Ashtown.

[16] Sir Alvary in 1968 also donated a collection of over 3000 books, pamphlets and periodicals, mainly relating to military and naval history, to Leeds Central Library in memory of his father Colonel F.R.T.

[17] He died on 18 April 1970 at age 76; and the London Gazette published a notice of Sir Alvary's death.