"I am surprised and touched by this big support," Niinisto told reporters in Helsinki, who secured over 62 per cent of the vote with nearly all the ballots counted.
Niinisto, 69, avoided the need for a second-round of voting and won outright yesterday, a first since Finland introduced a two-round presidential election by popular vote in 1994.
The politician who campaigned as an independent, has skilfully shifted the EU member state closer to NATO without antagonising Russia, with whom the Nordic nation shares the longest border in the bloc.
Niinisto's main rival Pekka Haavisto of the Green party won just 12 per cent of the votes.
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Conceding defeat, he told reporters in Helsinki: "I admit that Saulu Niinisto clearly won, warm congratulations to him."
Born into a working-class family in the southwestern Finnish town of Salo in August 1948, Niinisto -- the youngest of four children -- became a lawyer before entering politics as a member of the conservative National Coalition Party.