The Hon. Donald Mackenzie, Lord Mackenzie FRSE (22 June 1818 – 19 May 1875) was a Scottish law lord who served as a Senator of the College of Justice in Edinburgh.
Donald Mackenzie was born 22 June 1818, the only son of Capt. Donald Mackenzie, of the 21st Fusiliers and Margaret Robina Jamieson, daughter of the Rev. John Jamieson, DD, author of the Scottish National Dictionary. In early life the family lived at 39 George Square in south Edinburgh.
He studied at the Loretto School and the University of Edinburgh. He originally studied medicine, graduating MD at Edinburgh University in 1838, and became a licentiate of the Royal College of Physicians and also a Fellow of the Royal College of Surgeons. Mackenzie never practised as a physician, instead, yielding to his mother's wishes, he took up the study of the law.
Mackenzie was admitted as an advocate to the Scottish bar in 1842. He was Advocate Depute from 1854 to 1858, and again from 1859 to 1861. He served as the Sheriff of Fifeshire from 1861 to 1870. On 16 March 1870, he was appointed a Judge of the Court of Session in Scotland, under the name Lord Mackenzie.
Mackenzie's Edinburgh townhouse was at 24 Heriot Row: a fine Georgian townhouse in the New Town.