Sir George Mackenzie of Rosehaugh (1636/1638–1691) was a Scottish lawyer, Lord Advocate, essayist and legal writer.
Mackenzie, who was born in Dundee, was the son of Sir Simon Mackenzie of Lochslin (died c. 1666) and Elizabeth Bruce, daughter of the Reverend Peter Bruce, minister of St Leonard's, and Principal of St Leonard's Hall in the University of St Andrews. He was a grandson of Kenneth, Lord Mackenzie of Kintail and a nephew of George Mackenzie, 2nd Earl of Seaforth.
He was educated at the King's College, University of Aberdeen (which he entered in 1650), the University of St Andrews, and the University of Bourges in France.
Mackenzie was elected to the Faculty of Advocates in 1659, and spoke in defence at the trial of Archibald Campbell, Marquis of Argyll in 1661. He acted as justice-depute from 1661 to 1663, a post that involved him in extensive witch trials.
Mackenzie was knighted, and was a member of the Scottish Parliament for the County of Ross from 1669. In 1677 he became Lord Advocate, and a member of the Privy Council of Scotland.
As Lord Advocate he was the minister responsible for the persecuting policy of Charles II in Scotland against the Presbyterian Covenanters. After the Battle of Bothwell Bridge in 1679 Mackenzie imprisoned 1,200 Covenanters in a field next to Greyfriars Kirkyard. Some were executed, and hundreds died of maltreatment. His treatment of Covenanters gained him the nickname of "Bluidy Mackenzie". It has been argued that both he and Claverhouse kept to the letter of the law. It is unclear whether or not the epithet "Bluidy" is contemporary; it appears in The Heart of Midlothian (1818), given to Davie Deans. The language of blood prevails in the published testimony of Marion Harvey, hanged in 1681, who calls her blood onto Mackenzie, ""that excommunicate tyrant, George Mackenzie, the advocate", among others.