The Provisional Government of National Defence, also known as the State of Thessaloniki, was a parallel administration, set up in the city of Thessaloniki by former Prime Minister Eleftherios Venizelos and his supporters during World War I, in opposition and rivalry to the official royal government in Athens.

Eleftherios Kyriakou Venizelos was a Cretan Greek statesman and prominent leader of the Greek national liberation movement. He is noted for his contribution to the expansion of Greece and promotion of liberal-democratic policies. As leader of the Liberal Party, he held office as prime minister of Greece for over 12 years, spanning eight terms between 1910 and 1933. During his governance, Venizelos entered in diplomatic cooperation with the Great Powers and had profound influence on the internal and external affairs of Greece. He has therefore been labelled as "The Maker of Modern Greece" and is still widely known as the "Ethnarch".