Morgan John Winthrop O'Donovan (1893–1969), The O'Donovan, MC, held the position of O'Donovan of Clan Cahill from 1940 to his death in 1969. He was the son of Morgan William II O'Donovan and Mary Eleanor Barton, and was a descendant in the male line from Donal II O'Donovan, The O'Donovan of Clancahill, whom was the last chief of his sept inaugurated in the ancient Gaelic manner, with the White Rod, by his father in law MacCarthy Reagh, Prince of Carbery, circa 1584.