James Innes-Ker, 5th Duke of Roxburghe

James Innes-Ker, 5th Duke of Roxburghe (10 January 1736 – 19 July 1823) was a Scottish nobleman.

He was the eldest surviving son of Sir Henry Innes, 5th Baronet (c. 1711–1762), and Anne Drummonda Grant (1711–1771). He succeeded to the Baronetcy on his father's death. Through the Innes family, he was a descendant of Robert Ker, 1st Earl of Roxburghe, and in 1812 established his claim to the vacant Dukedom of Roxburghe.

The fight for the succession of the title encompassed seven years of constant litigation; according to one biography, "seldom have the lawyers met with a richer harvest. The courts of Edinburgh and London have revelled in conflicting claims, and the House of Lords has been disturbed by never-ending appeals." On the demise of the 3rd Duke, who had never married, his principal titles, and large and productive estates, devolved on William, 7th Lord Bellenden, who died shortly thereafter, without heirs. The succession was contested by Major-General Walter Ker and the Right Honorable William Drummond; and only at vast cost decided, on 11 May 1812, in favour of Sir James, as descended from Lady Innes, the third daughter of Hary, Lord Ker, son of the first Earl of Roxburghe.

Lord Bellenden was descended from the second Duke; General Ker claimed to be heir male of the first, and Mr. Drummond heir male of the second Earl, so that the issue turned on the construction of an entail, which gave the right to the female line. Other claimants included John Bellenden Ker (c. 1765–1842), famous as a wit and botanist and the author of Archaeology of Popular Phrases and Nursery Rhymes (1837), whose son was the legal reformer Charles Henry Bellenden Ker (c. 1785–1871). It is notable that 25 years later, Walter Ker's daughter Essex Ker was involved in litigation against her father's lawyers in connection with bonds issued to cover the costs of the succession litigation.

James took the name Innes-Ker, and became the 5th Duke of Roxburghe. He married twice, first to Mary Wray in 1769, who died in 1807. That same year he married Harriet Charlewood. He had one son by this second marriage, James, who succeeded to the Dukedom on his death.

Portraits of the Duke and his second Duchess were painted by Henry Raeburn, and hang in the entrance hall of the family seat of Floors Castle in the Scottish Borders.