Sir Robert Douglas, of Glenbervie, sixth baronet (1694–1770), genealogist, was the son of Sir Robert Douglas of Glenbervie (c.1662–1748), fourth baronet, and his second wife, Janet Paterson (1655–1750). His father, who inherited the baronetcy from a cousin in 1692, changed the name of his lands at Ardit, Fife, to Glenbervie, the name of the family's original barony in Kincardineshire. Details of Douglas's early life are few. The Glenbervie line was descended from a younger son of the fifth earl of Angus who died at Flodden in 1513. Born a younger son, Robert developed an abiding interest in the genealogy of Scotland's landed families that became his life's work.

Douglas is best known as the author of the most influential eighteenth-century account of the Scottish peerage. The field was pioneered by George Crawford's peerage of 1716. In 1759 Nathaniel Salmon's Short View of the Families of the Scottish Nobility appeared, noting that ‘there has been no good account of the Scottish Peerage for several years past’ (Salmon, iv). The ‘indefatigable and judicious Douglas’ (Almon, ii) spent many years gathering material. He gained access to numerous collections of family papers and public records, and also drew on the work of the antiquary Walter MacFarlane (d. 1767). Douglas gave peers a chance to correct or add to the entries on their families, if they could provide ‘sufficient Documents in Support of any Alteration made’ (Douglas, Peerage of Scotland, 1764, v). The Peerage of Scotland was published in Edinburgh in one folio volume in 1764, and was much acclaimed. Dedicated to James Douglas, fourteenth earl of Morton, the work was strongly supported by the Scottish aristocracy. The subscription list numbered 396, including some 56 peers (approximately sixty per cent of the Scottish peerage). Sections on individual families were excerpted and privately printed; that on the Wemyss family, for example, appeared in French in 1765. Having inherited his half-brother's baronetcy in 1764, Douglas reissued the peerage in 1768 with a new title-page denoting the author as ‘Sir Robert Douglas of Glenbervie, Bart.’

Douglas's peerage was generally accepted as authoritative in its day and served as the base for later efforts, particularly John Philp Wood's Peerage of Scotland, published in two volumes in 1813. Wood's Douglas, as the revision became known, remained the dominant reference work for the rest of the nineteenth century. In the early twentieth century Sir James Balfour Paul edited the massively expanded and revised Scots Peerage, Founded on Wood's Edition of Sir Robert Douglas's Peerage of Scotland (9 vols., 1904–14). As his subtitle indicated, Paul saw himself in direct succession to Douglas and Wood, and retained some of their wording.

During his lifetime Douglas also gathered much material for a companion work on the Scottish gentry, some of it with the help of James Cummyng (d. 1793), herald-painter and Lyon clerk depute. Though announced as forthcoming in 1767, the work was left in manuscript at Douglas's death. The first—and only—volume of The baronage of Scotland, containing an historical and genealogical account of the gentry of that kingdom appeared posthumously in 1796, with Douglas's name on the title-page and a notation that it had been completed by ‘other hands’. Douglas used the term ‘baronage’ in the Scottish sense of those who held land in free barony as tenants-in-chief of the crown. The work was well known long before publication, and at least parts of it circulated in manuscript during Sir Robert's lifetime. Indeed, his death notice in the Scots Magazine (1770, 24) described Douglas as ‘author of the Peerage and Baronage of Scotland’.

Douglas married three times. His first wife was Dorothea, daughter of Anthony Chester, attorney-general of Barbados. At some time before 1738 he married Margaret, daughter of Sir James MacDonald of Slate, sixth baronet. Finally, he wed Anne (d. 1770), daughter of Alexander Hay of Huntingdon. He died at Edinburgh on 24 April 1770, and was survived by Anne (who died on 17 September) and his only surviving son (from his second marriage) and heir, Alexander Douglas (1738–1812), a prominent physician.