President-elect Donald Trump announced Tuesday that his eldest son’s longtime fiancée, Kimberly Guilfoyle, will serve as US ambassador to Greece in his incoming administration — after sources spilled to The Post that Don Jr. and Guilfoyle recently split up.

“For many years, Kimberly has been a close friend and ally,” Trump, 78, posted on Truth Social.

“Her extensive experience and leadership in law, media, and politics along with her sharp intellect make her supremely qualified to represent the United States, and safeguard its interests abroad,” the president-elect added.

Trump argued that Guilfoyle, 55, is “perfectly suited to foster strong bilateral relations with Greece” and will advance US interests on issues “ranging from defense cooperation to trade and economic innovation.”

The president-elect’s 46-year-old son, Donald Trump Jr., popped the question to Guilfoyle on New Year’s Eve 2020, and the couple kept their engagement under wraps for nearly a year. 

But insiders revealed earlier Tuesday that Don Jr. and Guilfoyle’s relationship had been on the rocks for some time — with the two hinting at the rift in recent public spats at the incoming president’s West Palm Beach, Fla., resort.

“Don and Kimberly haven’t been getting along over the past year,” one source said. “They get argumentative at Mar-a-Lago in front of people. Nothing crazy, but you know when a couple is fighting. They bicker in public.”

Photos have also emerged of Don Jr. out and about with Palm Beach socialite Bettina Anderson, suggesting that he and Guilfoyle have ended their relationship and engagement. 

Guilfoyle, a former Fox News host, served as the chair of the Trump Victory Committee, the fundraising arm of the 45th president’s campaign, in 2020. 

She made frequent appearances at Trump campaign events this cycle and spoke at several of his rallies. Guilfoyle also addressed GOP delegates at the Republican National Convention in July. 

Guilfoyle, a San Francisco native, worked as a prosecutor in both the San Francisco and Los Angeles district attorney’s offices. 

She married Democratic California Gov. Gavin Newsom in 2001, when he was a San Francisco city supervisor, but the pair divorced in 2006. 

Guilfoyle said Tuesday that she was “honored to accept” Trump’s nomination, which requires Senate approval. 

“I’m honored to accept President Trump’s nomination to serve as the next Ambassador to Greece and I look forward to earning the support of the U.S. Senate,” she wrote on X. “President Trump’s historic victory is bringing hope and optimism to the American people and to freedom-loving allies across the world.”

“It was the democratic values born in Greece that helped shape the founding of America,” Guilfoyle added. “And now, we have an opportunity to honor that history by bringing better days here at home and abroad.”  

“As ambassador, I look forward to delivering on the Trump agenda, supporting our Greek allies, and ushering in a new era of peace and prosperity.”