Constantine II was the last king of which nation?

Constantine II ( born 2 June 1940) reigned as the last King of Greece, from 6 March 1964 until the abolition of the Greek monarchy on 1 June 1973. Constantine is the only son of King Paul and Queen Frederica of Greece. As his family was forced into exile during the Second World War, he spent the first years of his childhood in Egypt and South Africa. He returned to Greece with his family in 1946 during the Greek Civil War. King George II died in 1947, and Constantine's father became the new king, making Constantine the crown prince.

Source: Wikipedia