Sir Stanley Mordaunt Leathes, KCB, MA (7 May 1861 – 25 July 1938) was a British poet, economist, historian and senior Civil Service administrator, being the First Civil Service Commissioner from 1910 to 1927.
Leathes was born in London, the eldest son of the Hebrew scholar Stanley Leathes and his wife Matilda (née Butt). His younger brother was John Beresford Leathes, a distinguished physiologist who was elected a Fellow of the Royal Society in 1911.
Stanley Mordaunt Leathes was educated at Eton College between 1873 and 1880, holding a King's Scholarship. On leaving Eton, he went up to Trinity College, Cambridge, where in 1882 he was awarded a First in part one of the Classical Tripos and in 1884 another First in part two. Also in 1884 he received a notable prize, second Chancellor's Gold Medal. and took the degree of BA. While at Cambridge Leathes became a member of a small society of friends known as the T. A. F.; this was made up of members of King's College and Trinity College, who would meet every Sunday evening for supper. Other members included James Kenneth Stephen, Walter George Headlam, M. R. James,and Henry Babington Smith. In 1886 Leathes was elected a Fellow of Trinity and in 1888 proceeded by seniority to the degree of MA. He was a lecturer in History at his college from 1892 to 1903.