William Sinclair, 3rd Lord Sinclair

William Sinclair of Newburgh, Aberdeenshire (died 1487) was a Scottish nobleman and the 3rd Lord Sinclair. In The Scots Peerage by James Balfour Paul he is designated as the 2nd Lord Sinclair, but historian Roland Saint-Clair designates him the 3rd Lord Sinclair in reference to his descent from his grandfather, Henry II Sinclair, Earl of Orkney, the first Lord Sinclair. Roland Saint-Clair references this to an Act of the Scottish Parliament in which William Sinclair's son, Henry Sinclair, 4th Lord Sinclair, was made Lord Sinclair based on his descent from his great-grandfather, Henry II Sinclair, Earl of Orkney, the first Lord Sinclair. Bernard Burke, in his a Genealogical and Heraldic Dictionary of the Peerage and Baronetage of the British Empire, agrees with Roland Saint-Clair and says that Henry Sinclair was "in reality" the fourth holder of the title of Lord Sinclair.