Emmanuel Macron has appointed loyalist Sebastien Lecornu as his new Prime Minister.
The appointment comes after the resignation of Francois Bayrou after he lost a confidence vote.
Mr Lecornu will be the fifth Prime Minister to serve under Mr Macron in the past two years.
The new French Prime Minister rallied behind the President during his 2017 run, defying expectations that he might turn towards the left.
Mr Lecornu, 39, faces the challenging task of stabilising France's economy, something his predecessor failed to do.
Mr Bayrou's financial plan is at the centre of anger around France, with widespread protests planned for tomorrow.
The previous Prime Minister pledged to cut €44billion (£38.1billion) from the national budget, reduce two national holidays, freeze pensions and cut €5billion (£4.3billion) in health spending.
Mr Bayrou lost his confidence vote 364 to 194.
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Mr Lecornu takes over from Mr Bayrou
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By giving the position to Mr Lecornu, Mr Macron risks alienating the centre-left Socialist Party and leaves the President and his Government depending on Marine Le Pen's National Rally for support in parliament.
Mr Lecornu most recently served as the French President's defence minister, overseeing an increase in defence spending.
He helped decipher how Europe dealt with the security guarantees for Ukraine in the event that a peace deal with Russia is broken.
He entered politics canvassing for former President Nicolas Sarkozy when he was 16 and became mayor of a small town in Normandy at 18.
Mr Lecornu became the youngest Government adviser at the age of 22 under President Nicolas Sarkozy.
When the president was first elected in 2017, he left the conservative Les Republicains party to join Macron's centrist political movement.
The new Prime Minister sometimes had the ear of Marine Le Pen and her party chief, Jordan Bardella.
Mr Lecornu had a secret dinner with the pair last year.
Some 64 per cent of French people are calling for Mr Macron to resign, according to recent polling
| PAMr Macron has faced calls to resign after the resignation of his third Prime Minister.
Jean-Luc Melenchon, leader of France Unbowed, said on X: "Macron is now on the front line facing the people. He too must go."
French National Assembly Deputy Mathilde Panot stated that the French President must either resign or be impeached.
Some 64 per cent of French people would rather Mr Macron had resigned than name a new Prime Minister, according to a poll by Odoxa-Backbone for Le Figaro newspaper.