From his father's side he descended from the Kountouriotis, an Arvanite Hydriot family originally from the village of Kountoura, in the Megarid.

[1] He was the grandson of Georgios, a shipowner who like many members of his family, participated in the Greek War of Independence and served as Prime Minister of Greece under King Otto.

In 1900, Kountouriotis, as the commanding officer of the three-masted cruiser Navarchos Miaoulis, crossed the Atlantic Ocean and brought the flag of the Hellenic Navy to the New World for the very first time.

His orders were to present the flag of the Hellenic Navy to the 60,000 Greeks living in the U.S., but also to be the first exploratory mission of independent Greece.

Kountouriotis weighed in decisively in these discussions, proclaiming his confidence that even with the existing fleet, victory could be achieved, thanks to superior personnel.

His victories, due in large part to his daring but successful tactics, earned him the status of a national hero.

On the death of the young King Alexander in 1920, he was elected Regent of Greece by the Greek Parliament on 28 October by a vote of 137 to 3.

After King George II of Greece was deposed, he served as the first president (provisional) of the Second Hellenic Republic, from September 1925 until his resignation in March 1926; in opposition to General Pangalos' dictatorship.