Noble. The third, but eldest surviving son of James, 2nd Duke of Queensberry (1662 - 1711), Douglas was created Lord Douglas of Lockerbie, Dalveen and Thornhill, Viscount of Tiberris and Earl of Solway in 1706. He served as a Privy Counsellor and Lord of the Bedchamber to King George I and was appointed Vice Admiral of Scotland by George II, serving in this role from 1722 to 1729.
In 1720 he married Catherine, daughter the 4th Earl of Clarendon, who was a famous beauty although eccentric. She was the friend of many of the wits and writers of her day, including John Gay, Alexander Pope, Jonathan Swift and Horace Walpole. Douglas's support for Gay and his Beggar's Opera, which greatly offended the king, led to his being banished from court. Douglas associated himself with Frederick, the Prince of Wales, who was estranged from his father. When Frederick's son succeeded as George III Queensberry's position was restored. He served as Keeper of the Great Seal of Scotland (1761-63) and was Lord Justice General from 1763 until his death.
He died in London. His sons having pre-deceased him, his British titles died with him. However his Scottish titles, including the Dukedom of Queensberry, were inherited by his cousin, who became known as the 'Old Q'. Douglas is remembered by the Queensberry Monument in Dumfries.