Constantine II (Greek: Κωνσταντῖνος Β΄, Konstantínos II) was the last King of Greece, reigning from 1964 until the abolition of the Greek monarchy in 1973.
He acceded as king following the death of his father King Paul in March 1964. Later that year he married Princess Anne-Marie of Denmark with whom he eventually had five children. Although the accession of the young monarch was initially regarded auspiciously, his reign soon became controversial: Constantine's involvement in the Apostasia of July 1965 created unrest among sections of the population and aggravated the ongoing political instability that culminated in the Colonels' Coup of 21 April 1967.
The coup was successful, leaving Constantine, as head of state, little room to manoeuvre as he had no loyal military forces on which to rely. As a result, he reluctantly agreed to inaugurate the putschist government on the condition that it be made up largely of civilian ministers. On 13 December 1967, he was forced to flee the country, following an abortive counter-coup against the junta. He remained the head of state in exile until 1 June 1973, when the junta abolished the monarchy.
This abolition was confirmed after the fall of the junta by a plebiscite on 8 December 1974, which established the Third Hellenic Republic. Constantine, who was not allowed to return to Greece to campaign, accepted the results of the plebiscite.
King Constantine II was styled "Βασιλεύς τῶν Ἑλλήνων" (King of the Hellenes).