Israeli Prime Minister Benjamin Netanyahu called it “history’s greatest comeback.”

Ukrainian President Volodymyr Zelenskyy said Republican Donald Trump’s victory in Tuesday’s presidential election was “impressive,” and that a Trump administration could help bring about a “just peace” in the Ukraine-Russia war.

South Korean President Yoon Suk Yeol said the U.S.-South Korea relationship “will shine brighter” with Mr. Trump in office.

Across the world, heads of state pledged to work with the incoming president. Some seemed eager for new U.S. leadership at a time of raging wars in Europe and the Middle East, and as the alliance of U.S. adversaries including China, Russia, Iran and North Korea grows stronger.

China, as it has throughout the campaign, tried to strike a neutral tone on the U.S. race, despite a history of tense relations with Mr. Trump during his first term in the White House.

“China hopes for peaceful and stable coexistence with the U.S. on the basis of mutual benefits and respect,” Chinese Foreign Ministry spokeswoman Mao Ning told a regular news briefing in Beijing Wednesday.

The vote, she said, was a domestic political issue, China “respects any choice of the American people.”

In Moscow, Kremlin spokesman Dmitry Peskov said he was not aware of any plans for Mr. Putin to speak to Mr. Trump or to offer his congratulations. He also took aim at America’s strong military backing for Ukraine since Russia’s invasion of its neighbor in February 2022. 

“Let’s not forget that we’re talking about an unfriendly country that’s both directly and indirectly involved in a war against our nation,” Mr. Peskov said, according to English-language media reports, though he did give a nod to Mr. Trump’s stated desire to end the conflict.

“Since the United States fuels and participates in this conflict, then yes the United States is capable of changing the trajectory of this foreign policy,” Mr. Peskov said. “Whether it will be done and how it will be done, you and I will see after January” when Mr. Trump is expected to be inaugurated.

Former President Dmitry Medvedev, now one of Mr. Putin’s most hawkish security advisers, said he saw at least some promise in Mr. Trump’s victory.

“Trump has one useful quality for us,” Mr. Medvedev wrote on the Telegram messaging app. “As a businessman to the core, he mortally dislikes spending money on various hangers-on and stupid hanger-on allies, on bad charity projects and on voracious international organizations.”

Reactions from world leaders began trickling in Wednesday morning after Mr. Trump was projected to defeat Vice President Kamala Harris, capping a stunning political comeback with decisive wins in several key swing states.

Mr. Netanyahu, who has had a tense relationship with President Biden amid harsh criticism from the administration over how Israel has conducted its war against Hamas in the Gaza Strip, framed Mr. Trump’s victory in broad, historic terms.

“Congratulations on history’s greatest comeback!” he wrote in a post on X.

“Your historic return to the White House offers a new beginning for America and a powerful recommitment to the great alliance between Israel and America,” Mr. Netanyahu said. “This is a huge victory!”

In a lengthy social media post, Mr. Zelenskyy recounted his “great meeting” with Mr. Trump in September. And he said that Mr. Trump, who has pledged to end the Russia-Ukraine war quickly upon taking office, has the kind of principles that could bring about peace.

“I appreciate President Trump’s commitment to the ’peace through strength’ approach in global affairs. This is exactly the principle that can practically bring just peace in Ukraine closer. I am hopeful that we will put it into action together,” Mr. Zelenskyy said. 

“We look forward to an era of a strong United States of America under President Trump’s decisive leadership,” he wrote on X. “We rely on continued strong bipartisan support for Ukraine in the United States.”

The Trump-Zelenskyy dynamic is complicated by the fact that Mr. Trump was impeached by the House in 2020 for what critics say was an inappropriate push for Mr. Zelenskyy’s administration to investigate Biden family business dealings in Ukraine. Mr. Trump also argues that his relationship with Russian President Vladimir Putin could help facilitate an end to the conflict.

Elsewhere in Europe, key leaders congratulated Mr. Trump and seemed eager to work with him.

“The biggest comeback in U.S. political history! Congratulations to President @realDonaldTrump on his enormous win. A much needed victory for the world!” Hungarian Prime Minister Viktor Orban, one of Mr. Trump’s closest European allies, wrote on social media.

French President Emmanuel Macron said the U.S. and France can work closely together under a Trump presidency.

“Congratulations President Donald Trump,” the French president said on social media. “Ready to work together as we have done for four years. With your convictions and with mine. With respect and ambition. For more peace and prosperity.”

In his own social media post, Mr. Yoon said the U.S.-South Korea relationship will remain strong.

“Congratulations to @realDonaldTrump! Under your strong leadership, the future of the ROK-U.S. alliance and America will shine brighter. Look forward to working closely with you,” he said in a social media post.