The decision was a foregone conclusion as the Georgian constitution does not allow dual nationality.
"Based on the law of Georgian citizenship, President Giorgi Margvelashvili signed a decree terminating Mikheil Saakashvili's citizenship due to his acquisition of a foreign country's nationality," Margvelashvili's press service said in a statement on Friday.
Saakashvili acquired a Ukrainian passport after President Petro Poroshenko named him governor in May this yearof the strategically important port of Odessa just across the Black Sea from the Crimea peninsula.
Friday's decree is "yet another example of employing legal instruments for political persecution," said Nugzar Tsiklauri, an opposition member of parliament in Georgia.
The appointment of the fervently pro-Western Saakashvili was viewed as a signal to Russia that Ukraine remained set on a pro-European course despite the crisis in its eastern regions.
The 47-year-old former Georgian president came to power after the famous Rose Revolution in 2003 and soon became Moscow's arch-enemy for his pro-West stance.
He is credited by the West for pulling the small ex-Soviet state out of Russia's influence. Under Saakashvili, Georgia also fought a brief war with Russia in 2008, in which the country lost control of two of its separatist regions.
Georgia meanwhile has issued an arrest warrant against Saakashvili on charges that he abused his powers. The former Georgian president insists the charges are politically motivated.
Several of Saakashvili's top allies in Georgia have been investigated and some jailed after the defeat of his United National Movement (UNM) party in parliamentary and presidential elections in 2012 and 2013.
ap/jm (AFP, Reuters)