Bourne previously served as Minister of Environment, Transport, and Labor.
She will lead a French government likely tasked with implementing President Macron’s election campaign priorities: pension reform and broadening policies designed to combat climate change.
According to the Elysee, he “entrusted Bourne with the formation of the government.”
She dedicated her nomination to “Every Little Girl,” during a gala Monday to mark the transition of power.
“Follow your dreams all the way,” Burnie said in a letter. “Nothing should hinder the struggle for the position of women in society.”
Earlier on Monday, the Elysee Palace announced that Castex had submitted his resignation.
The former mayor of his small town of Prades in southwest France, was a little-known figure when he became prime minister in July 2020. He has gone on to lead France’s response to the Covid-19 pandemic.