Sir Rupert Iain Kay Moncreiffe of that Ilk, 11th Baronet, CVO, QC, Ph.D. was a Scottish officer in the British Army and a genealogist.
Educated at Stowe School, Heidelberg, and Christ Church, Oxford, he served in World War II in the Scots Guards, served as attaché at the British embassy in Moscow, and then studied Scots Law at the University of Edinburgh, where he took a Ph.D. with a thesis on the Scots law of succession to peerages.