Justin Huntly McCarthy (1859 - 20 March 1936) was an Irish author, historian, and nationalist politician. He was a Member of Parliament (MP) from 1884 to 1892, taking his seat in the House of Commons of the United Kingdom. He was the son of Justin McCarthy (1830-1912). Since both father and son were authors, historians, and Members of Parliament, they are sometimes confused in lists and compilations. McCarthy wrote various novels, plays, poetical pieces and short histories. He was briefly married to the actress Cissie Loftus. They married in Edinburgh in 1894, and though they divorced in 1899, she originated the role of Katherine de Vaucelles, the heroine in If I Were King in 1901.