Rt Hon Hugh Pattison Macmillan, Baron Macmillan of Aberfeldy FRSE GCVO PC QC (20 February 1873 – 5 September 1952) was a Scottish advocate, judge, Parliamentarian and civil servant.
He was born in Glasgow, the son of the Rev Hugh Macmillan DD FRSE (1833-1903) and Jane Patison (1833-1922). His father was minister of St Peter's Free Church in Glasgow. The family moved to 70 Union Street in Greenock in 1878.
Hugh was educated at Collegiate School, Greenock from 1878, then studied at the University of Edinburgh (M.A. 1st in class honours in philosophy, 1893 Bruce of Grangehill and Falkland Scholarship) and the University of Glasgow (LLB). He was indentured for three years to the firm Cowan, Fraser and Clapperton while he studied the Law, in which he distinguished himself by winning the Cunningham Scholarship for Conveyancing in the year 1896. He was admitted to the Faculty of Advocates in 1897 with public defence of assigned Thesis on De diversis regulis juris antiqui, and later became King's Counsel in 1912. He wrote for a time articles in conveyancing for Green's Encyclopedia of Scots Law, and was Editor of the quarterly Juridical Review between 1900 and 1907.
During the First World War Macmillan served as Assistant Director of Intelligence for the Ministry of Information.
Macmillan suffered an illness, and surgery thereon, in 1917, at which time he decided to cease his nascent political career (then in abeyance for the duration of the Great War). In October 1922, he was asked by Bonar Law to become the Solicitor-General for Scotland, which he declined because of his political stripe.