It's after the resignation of Edouard Philippe who has been in the post for three years.
Mr Castex, 55, is relatively unknown in France, although he is a senior civil servant.
The new Prime Minister has been a key player in the government's response to the Covid-19 pandemic.
Trump says deal reached to disarm Hamas, Israeli support for plan remains uncertain
US President Donald Trump said talks in Cairo between mediators and Hamas leaders on Thursday have led to a phased disarmament agreement in Gaza.
Sri Lanka's former police chief sentenced to death over 2019 Easter bombings
Sri Lanka's former police chief Pujith Jayasundara and former senior defence official Hemasiri Fernando were sentenced to death on Friday over the 2019 Easter bombings that killed 279 people, local media reported.
Spain says migrants are returning to Ceuta after 57 killed in border rush
Spain said on Friday it had reversed a huge rush of migrants into a Spanish enclave in North Africa, with most of the more than 50,000 people who had crossed the border by land and sea already heading back voluntarily.
Kuwait intercepts hostile drones after attacks on vital, military sites
Kuwait's Armed Forces intercepted and destroyed drones that entered its airspace on Friday morning, adding there was material damage due to falling debris but no casualties.
The UAE Year Of Award has been launched to honour individuals and institutions who create meaningful impact and strengthen a culture of community action to make each annual "UAE Year Of" theme into a lasting national legacy.
Sheikh Abdullah bin Zayed Al Nahyan, UAE Deputy Prime Minister and Minister of Foreign Affairs, has discussed ways to strengthen bilateral ties and boost cooperation across key sectors during talks with UK Foreign Secretary in London.
His Highness Sheikh Hamdan bin Mohammed bin Rashid Al Maktoum, Dubai's Crown Prince, Deputy Prime Minister and Minister of Defence, has attended a GCC joint military exercise at the start of his official visit in Bahrain.
