The Polish former prime minister will serve a second term in his new European role. His home country Poland, now governed by fierce opponents of Tusk's, had sought to block him - Tusk himself acknowledged the "paradox."
Former Polish Prime Minister Donald Tusk was re-elected as President of the European Council on Thursday in Brussels.
Luxembourg's prime minister, Xavier Bettel, tweeted in Latin, saying: "We have a European Council president. Good luck, Donald."
Bettel was playing on the language used to announce a new pope's choosing.
Tusk took to Twitter to express his gratitude for the result. "Thank you for keeping your fingers crossed and for your heart-felt support. It helped!"
The former prime minister of Poland acknowledged how unusual it was to face opposition from his home country, but said the vote displayed European unity.
"It may sound like a paradox because of the context, but anyway, your decision is an expression of our unity today. I will work with all of you without any exceptions because I am truly devoted to a united Europe," he said.
Polish government apoplectic
Tusk received strong support from most of the leaders of the 28-nation bloc. However, Poland's ruling PiS ("Law and Justice") party - which is rather lukewarm on the EU itself - is a staunch opponent of Tusk's and had sought to block his re-election to the role.
Beata Mazurek, a spokeswoman for the PiS party, said Tusk's re-election will "influence the way that the union will function in the future. It will no longer be a union of unity."
Poland was the only country to vote against Tusk, according to Czech Prime Minister Bohuslav Sobotka.
PiS party leader Jaroslaw Kaczynski did not support the results, saying, "The rule that high-ranking officials should have the backing of their country was broken."
Kaczynski said any talk of Poland wishing to leave the EU was "nonsense."
Poland's foreign minister, Witold Waszczykowski, said that "a very dangerous European relationship is being born," and that, given Tusk's appointment, "we know now that it is a Union under Berlin's diktat."
Tusk will serve a second term, lasting two and a half years, as European Council president. He took up the role on December 1, 2014. Tusk is responsible for chairing European Council meetings and representing the EU at international summits, typically along with the European Commission president, Jean-Claude Juncker.
The 59-year-old could prove a critical component to EU talks in preparation for the UK's departure from the EU - not least given the preponderance of Polish people living in Britain.
Other items on the agenda
The two-day summit in Brussels will later touch on migration, security, the western Balkans and the economy in the bloc.
Thursday talks are expected to see the introduction of new free trade pacts, as well as continued support in the western Balkan states.
The European Council will also look at plans to reduce illegal migration from Libya to Italy. On Friday, the council will meet without British Prime Minister Theresa May in order to prepare for a "unity" summit that will be held in Rome on March 25, the 60th anniversary of the signing of the Treaty of Rome, which established the predecessor to the modern-day EU.
Poland has vowed to block the summit's final statement in protest of Tusk's re-election. The statement must receive unanimous agreement in order for the results of the summit to take effect.
kbd/msh (AFP, AP, Reuters)