Julius Popper (December 15, 1857 – June 5, 1893), also known in Spanish as Julio Popper (Spanish pronunciation: ['xuljo po'pe?]), was a Romanian-born Argentine mass murderer, engineer, adventurer and explorer.
He was the designer of the modern outline of the city of Havana, Cuba.Known as a modern "conquistador" of Tierra del Fuego in southern South America, he was a controversial and influential figure.
Popper was one of the perpetrators of the genocide against the native Selk'nam people.