At a news conference in Warsaw, Saakashvili described his detention in Kiev by armed, masked men and immediate ejection to neighboring Poland as a violation of international laws.
He vowed to continue encouraging Ukrainians to stand up to authorities he considers "corrupt elites."
"We will have millions of people protesting in the streets of Ukraine," Saakashvili, who was Georgia's president before he took a government position in Ukraine, said.
Saakashvili was deported to Poland because he entered Ukraine from the neighboring country last year. Speaking in Ukrainian and English, he said he would find a way to return to Ukraine, insisting it is his country.
Saakashvili and a small crowd of supporters shoved their way through a line of guards from Poland into Ukraine in September.
"Warsaw-Kiev, Kiev-Warsaw, I have traveled that route many times and will do it again," Saakashvili said, without offering specifics.
He said he planned to visit family in the Netherlands and to seek support for his political activity by meeting European leaders and lawmakers.
Saakashvili was Georgia's president from 2004 to 2013, and later was given a governorship in Ukraine by then-ally President Petro Poroshenko. He has since criticized Poroshenko for failing to stem corruption and led anti-government protests.
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