Incumbent Polish President Bronislaw Komorowski, facing a surprisingly strong electoral challenge from conservative Andrzej Duda, conceded defeat Sunday.
His concession came a short while after voting ended and a key exit poll showed him trailing by a 53-47 percent margin.
Komorowski said: "I wish him a successful presidency because I wish well for Poland.''
A 62-year-old historian and former defense minister, Mr. Komorowski campaigned for a second term largely on national security issues, including heightened tensions with Russia over the Ukraine crisis. He was forced
into Sunday's runoff vote after finishing second to Mr. Duda in first-round polls May 10.
The victory for the 43-year-old Mr. Duda marks the first major electoral win for the opposition Law and Justice party that nominated him.
"Thank you to Mr. President Bronislaw Komorowski for the rivalry in this election campaign, for the congratulations which he passed to me.''
The win ends more than eight years of political dominance by the incumbent's Civic Platform party. It also sets the stage for what analysts predict will be a tight re-election battle later this year between Prime Minister Ewa Kopacz - a Komorowski ally -- and the conservative opposition.
UN-Led Peace Talks for Yemen in Doubt
A U.N.-brokered peace conference for Yemen scheduled to take place later this week appeared in doubt Monday with Yemeni officials saying the talks had been postponed.
There was no immediate public confirmation from the U.N. that Thursday's meeting would be delayed.
Yemen's President Abdu Rabu Mansour Hadi, who fled to Saudi Arabia two months ago, has demanded Houthi rebels abide by a U.N. Security Council resolution and withdraw from the territory they have seized before the talks can proceed.
Yemeni officials on Monday cited those demands and described the conference as indefinitely postponed.
U.N. Secretary-General Ban Ki-moon announced the talks last week, urging both sides to participate without any preconditions and to resume working toward a political resolution to the country's crisis.