Prince Philip of Greece and Denmark was born in Mon Repos on the Greek island of Corfu on 10 June 1921, the only son and fifth and final child of Prince Andrew of Greece and Denmark and Princess Alice of Battenberg. Philip's four elder sisters were Margarita, Theodora, Cecilie, and Sophie. He was baptised in the Greek Orthodox rite at St. George's Church in the Old Fortress in Corfu. His godparents were his paternal grandmother Queen Olga of Greece, represented by Princess Olga of Greece and Denmark, and Alexandros S. Kokotos, the Mayor of Corfu, representing the people of Corfu.
Shortly after Philip's birth, his maternal grandfather, Prince Louis of Battenberg, then known as Louis Mountbatten, Marquess of Milford Haven, died in London. Louis was a naturalised British citizen, who, after a career in the Royal Navy, had renounced his German titles and adopted the surname Mountbatten, an Anglicized version of Battenberg, during the First World War due to Anti-German sentiment in Great Britain. After visiting London for the memorial, Philip and his mother returned to Greece where Prince Andrew had remained behind to command an army division embroiled in the Greco-Turkish War (1919–1922).
The war went badly for Greece, and the Turks made large gains. On 22 September 1922, Philip's uncle, King Constantine I, was forced to abdicate and the new military government arrested Prince Andrew, along with others. The commander of the army, General Georgios Hatzianestis, and five senior politicians were executed. Prince Andrew's life was believed to be in danger, and Alice was under surveillance. In December, a revolutionary court banished Prince Andrew from Greece for life. The British naval vessel HMS Calypso evacuated Prince Andrew's family, with Philip carried to safety in a cot made from a fruit box. Philip's family went to France, where they settled in the Paris suburb of Saint-Cloud in a house lent to them by his wealthy aunt, Princess George of Greece and Denmark.
Because Philip left Greece as a baby, he does not have a strong grasp of the Greek language. In 1992, he said that he "could understand a certain amount". Philip has stated that he has thought of himself as Danish, and his family spoke English, French, and German. Philip, who in his youth was known for his charm, was linked to a number of women including Osla Benning.