Garegin or Karekin Pastermadjian (classical ), better known by his "nom de guerre" Armen Garo or Armen Karo (Արմէն Գարօ; 9 February 1872 – 23 March 1923) was an Armenian nationalist activist and politician. Armen Karo was a leading member of the Armenian Revolutionary Federation for more than two decades. He was one of the masterminds of the 1896 occupation of the Ottoman Bank in response to the Hamidian massacres and Operation Nemesis, in which several perpetrators of the Armenian genocide were assassinated. Between 1918 and 1920 he served as the first ambassador to the United States from the First Republic of Armenia.