Austria's far-right presidential candidate Norbert Hofer conceded defeat to Green party rival Alexander Van der Bellen in a post on Facebook on Monday.
"Of course I am very sad today. I would have liked to have kept watch over this wonderful country as president," the 45-year-old Freedom Party politician writes.
The official results of the run-off election have yet to be announced, with absentee ballots set to decide the election after Sunday's vote resulted in a dead heat between the two candidates.
Senior Freedom Party legislator Hofer had entered the race as the favourite after having won the first round of elections in April.
Despite his apparent loss to Van der Bellen, the strong support for Hofer's eurosceptic and anti-immigration platform signals growing public acceptance of such positions in Europe.