Alda Mary Milner-Barry (5 July 1893 – 26 March 1938)^[1] was a British cryptoanalyst and academic. She was a fellow and vice-principal of Newnham College, Cambridge, and part of MI1b, the British military intelligence unit of the War Office in World War I.^[2][3]

Alda Milner-Barry was born in 1893, the daughter of Edward Leopold Milner-Barry, Professor of Modern Languages at the University of Bangor, and his wife Edith Mary Milner-Barry (née Besant).^[4][5] Her grandfather was William H. Besant, a mathematical fellow of St John's College, Cambridge.^[2] Her aunt Alda Marguerite Milner-Barry was an author, lecturer, and hymnwriter.^[6] Her younger brother, Stuart Milner-Barry, was a renowned chess player and would become a codebreaker at Bletchley Park during World War II.^[2][4][7]

While an undergraduate at Newnham College, Cambridge,^[2] Alda Milner-Barry covered her father's lessons at the University of Bangor while he was working as a translator in the British Admiralty.^[5][8] She completed the Medieval and Modern Languages tripos at Cambridge in two years, instead of the usual three, in 1914.^[9] In 1916, she graduated with first class honours in English and German. She immediately took up work as a translator in the Intelligence Department of the War Office.^[2] In around 1917, Milner-Barry was the interim Professor of German at University College Galway for a year. She then went to MI1b, where she was appointed deputy to codebreaker Emily Anderson.^[2]

From 1920 to 1934, she was a lecturer in English at the University of Birmingham and, from 1934 to 1938, the tutor of Sidgwick Hall, Newnham College.^[10][11] She became vice-principal of the college, remaining in that position until her death in 1938, at the age of 44, at a nursing home in Cambridgeshire.^[2][7]

• Milner-Barry, Alda (1926). "A Note on the Early Literary Relations of Oliver Goldsmith and Thomas Percy". The Review of English Studies. 2 (5): 51–61. doi:10.1093/res/os-II.5.51. ISSN 0034-6551. JSTOR 507645.
• Milner-Barry, Alda (1927). "Review of The History and Sources of Percy's Memoir of Goldsmith". The Review of English Studies. 3 (10): 232–234. doi:10.1093/res/os-III.10.232. ISSN 0034-6551. JSTOR 508289.