Princess Irene of Greece and Denmark (Greek: Irini) (13 February 1904 - 14 April 1947) was the fifth child and second daughter of Constantine I of Greece and his wife, the former Princess Sophie of Prussia.

Her paternal grandparents were George I of Greece and Olga Konstantinovna of Russia. Her maternal grandparents were Friedrich III, German Emperor, and his Empress consort Victoria. Victoria was a daughter of Prince Albert of Saxe-Coburg and Gotha and Queen regnant Victoria of the United Kingdom.

Irene was born in Athens, preceded in birth by three brothers, Prince George (1890), Prince Alexander (1893) and Prince Paul (1901), and one sister, Princess Helen (1896). Another sister, Princess Katherine was born in 1913.

On 1 July 1939, Princess Irene married Prince Aimone of Savoy, Duke of Spoleto (b. 9 March 1900 in Florence, Italy) They had one child:

Prince Amadeo Umberto Constantino Giorgio Paolo Elena Maria Fiorenzo Zvonimir of Savoy, born 27 September 1943 married (1) Princess Claude Marie de Bourbon-Orléans (b. 1943) on 22 July 1964 in Sintra, Portugal, divorced in 1982 and had issue.

Princess Bianca Irene Olga Elena Isabella of Savoy (b. 2 April 1966)

Prince Aimone Umberto Emanuele Filiberto, Duke of Apulia (b. 13 October 1967)

Princess Mafalda Giovanna of Savoy (b. 20 September 1969)

Prince Amadeo married (2) Donna Silvia Paterno (b. 31 December 1953) on 30 March 1987 in Bagheria, Sicily, no issue. In addition to three children from his first marriage, Amadeo also has one son, Pietro Incisa della Rochetta, born in 1967, by Nerina Corsini, the wife of Enrico Incisa della Rochetta. He is expecting a fifth child, also illegitimate, by Kyara van Ellinkhuizen. Kyara told the press that the baby will be a girl and that will be named Ginevra. Pre-birth examinations have shown that the girl has Down Syndrome.

Prince Aimone became 4th Duke of Aosta on 3 March 1942, following the death of his elder brother Prince Amadeo, 3rd Duke of Aosta. On 18 May 1941, taking the name Tomislav II, he was proclaimed King of the Independent State of Croatia, a German/Italian puppet state covering most of Croatia and Bosnia and Herzegovina. He never had any power or even set foot on the territory of the state, and subsequently abandoned the crown on 12 October 1943, after the Italian withdrawal from the war. Prince Aimone died on 29 January 1948 in Buenos Aires. Upon his death, his son succeeded him as the 5th Duke of Aosta.

Princess Irene died on 14 April 1947 in Fiesole. She was forty-three.