“We will succeed... because nothing is impossible,” said Sébastien Lecornu as he gave his maiden speech as France’s Prime Minister at his handover ceremony in Paris on September 9. He was appointed Premier by President Emmanuel Macron in less than 24 hours after the fall of François Bayrou’s government. Mr. Lecornu, 39, is now the country’s fifth Prime Minister in under two years.

Born on June 11, 1986 in Eaubonne, Val-d’Oise, Sébastien Lecornu is the son of an aeronautics factory technician and a medical secretary. His modest background, rooted in the small town of Vernon in Normandy, shaped his political outlook. “Unfortunately, I was born old,” he once joked, a self-effacing remark that hinted at both his receding hairline and the weight of early responsibilities. Politics, he says, was always present. “I never imagined myself holding government office so early,” Mr. Lecornu said.