Conrad Fulke Thomond O'Brien-ffrench, 2nd Marquis de Castelthomond (19 November 1893 – 23 October 1986) was a distinguished British Secret Intelligence Officer, Captain in the Tipperary Rangers of the Royal Irish Regiment and 16th The Queen's Lancers in World War I, and Mountie for the Royal North-West Mounted Police. He was also an accomplished artist, linguist, mountaineer, skier, and author.