John Sholto Douglas (1844-1900) was an eccentric Scottish nobleman, the 9th Marquess of Queensberry and Viscount Drumlanrig. He is remembered for lending his name to the "Marquess of Queensberry rules" that formed the basis of modern boxing.

He inherited the Queensberry title in 1858 from Archibald William Douglas. He was a famous patron of sport and a noted boxing enthusiast; he was one of the founders of the Amateur Athletic Club in 1860.

In March 1895 the Marquess was sued for defamatory libel by Oscar Wilde, who Douglas had intimated was a "somdomite" (sic): Douglas made the accusation because he was angered over Wilde's relationship with his son, Alfred. Soon after the trial opened, the libel case was withdrawn, but Wilde was later convicted of gross indecency under the Criminal Law Amendment Act of 1895.

Douglas died in London. He had married the daughter of Alfred Montgomery, and his title passed to his son Percy Sholto Douglas.