A wider cabinet reshuffle is expected this week as Macron seeks to sharpen his team for the final three years of his presidency.
“The president of the republic appointed Mr Gabriel Attal prime minister, and tasked him with forming a government,” a presidential statement said.
Attal is set to bring a major change of style to the office of the prime minister following Borne, only the second woman to lead the French government.
Her austere and no-nonsense demeanour won respect from colleagues but not necessarily popularity from the public, whereas Attal is the most popular figure in government after his stint at the politically crucial education ministry.
The appointment of Attal had been expected after Borne’s resignation on Monday, and the absence of the swift announcement fuelled talk that heavyweight government figures were unhappy over Attal’s meteoric promotion.
However, sources close to those said to be behind the tensions, including Interior Minister Gérald Darmanin and Finance Minister Bruno Le Maire, vehemently denied this.
Borne’s resignation letter to Macron, a copy of which was seen by AFP, hinted that she would have preferred to stay in her job.
“While I must present the resignation of my government, I wanted to tell you how passionate I was about this mission,” she wrote.
Commentators see the reshuffle as essential to relaunch Macron’s centrist presidency for its last three years and prevent him becoming a “lame duck” leader after a series of crises.
Since he defeated the far-right to win a second term in 2022, Macron has faced protests over unpopular pension reforms, the loss of his overall majority in parliamentary elections and controversy over immigration legislation.
While Macron cannot run again in 2027 presidential elections, relaunching his government is seen as crucial to help prevent Le Pen becoming president.
The conservative daily Le Figaro said Borne was leaving a political situation “that remains as fragile as ever.”
“Changing a face at the top doesn’t change the overall picture,” the newspaper said, adding Borne’s successor was facing “an overwhelming pile of political emergencies” including the task to unite a fragmented nation.
Under the French system, the president sets general policies and the prime minister is responsible for day-to-day government management, meaning the latter often pays the price when an administration runs into turbulence.
European Parliament elections in June will pose a major test, with Macron’s Renaissance party risking embarrassment at the hands of Le Pen’s National Rally (RN).
He will go toe-to-toe ahead of the European elections with another rising star of French politics, the even younger Jordan Bardella, just 28, who is now party leader of the far-right RN.
Constitutional expert Benjamin Morel told AFP that Attal’s appointment signals a “very offensive strategy with a view to the European elections” in June.
But political scientist Bruno Cautres said he would “not solve the problem of the majority, nor the main problem which is where the mandate [of Macron] is heading”.
Other key posts are also subject to uncertainty, in particular that of Darmanin, 41, a right-winger said to covet the post of foreign minister held by Catherine Colonna.
The new head of government will be the fourth prime minister since 2017 under Macron, who is accused by critics of micromanaging and centralising power in the Elysee.