Alexander I, King of the Hellenes, ruled Greece from 1917-1920.

He was born on 21 July (O.S.) = 2 August 1893 (N.S.) at Tatoi near Athens, the son of Constantine I, King of the Hellenes and his wife, formerly Princess Sophie of Prussia.

When his father left the country in 1917, he was named acting king.

On 4 November 1919 he married Aspasia Manos (1896-1972), daughter of Colonel Petros Manos. Their only child, born posthumously, was Princess Alexandra of Greece (1921-1993), who married Peter II, King of Yugoslavia.

He died on 25 October 1920 at Athens, of sepsis, after he had been bitten by a pet monkey.