Sir William Macleod Bannatyne (26 January 1743 – 30 November 1833) was a distinguished Scottish lawyer and judge.
The son of Mr. Roderick Macleod, writer to the signet and Isabel (fl. 1736–1744), daughter of Hector Bannatyne of Kames. He received a liberal education, and was admitted advocate, January 22, 1765. On the death of Lord Swinton, in 1799, he was promoted to the bench, and took his seat as Lord Bannatyne.
Among his intimate friends were Henry Mackenzie, Robert Cullen, William Craig, Hugh Blair, Erskine and Alexander Abercromby. He was a contributor to the Mirror and Lounger, about the end of the eighteenth century.
He assumed the name of Bannatyne when he succeeded, through his mother to the estate of Kames in the Isle of Bute. He extended Kames Castle by the addition of a fine mansion house in the early eighteenth century. He sold the Kames estate in 1812 to James Hamilton, and moved to Edinburgh.
He retired in 1823, when he was knighted. He died at his home, Whiteford House on the Canongate in Edinburgh in 1833.
He collected a library of historical, genealogical, and antiquarian works, and at its sale in 1834, a set of the Bannatyne publications was purchased for Sir John Hay, Baronet of Smithfield and Haystown, for one hundred and sixty-eight pounds sterling.