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 not satisfied with Iran's latest proposal, will not 'leave war early'
US President Donald Trump said on Friday he was not satisfied with the latest Iranian proposal for talks on the war, while Iran's foreign minister said Tehran was ready for diplomacy if the United States changes its approach.
Iran sends proposal for negotiations with US to mediator Pakistan
Tehran has submitted its latest proposal for negotiations with the United States, Iranian state media and a Pakistani official said on Friday, a move that could offer hope for breaking a deadlock in efforts to end the Iran war.
Kenya flood death toll hits 10 as dam overflow risk raises alarm
At least 10 people have died across Kenya after heavy rains triggered flooding and landslides in several regions, police said, as authorities warned rising river levels could threaten communities downstream from a major hydropower dam system.
Iran threatens painful response if US renews attacks
Iran said on Thursday it would respond with "long and painful strikes" on US positions if Washington renewed attacks and restated its claim to the Strait of Hormuz, complicating US plans for a coalition to reopen the waterway.
His Highness Sheikh Hamdan bin Mohammed bin Rashid Al Maktoum, Crown Prince of Dubai, Deputy Prime Minister, and Minister of Defence, has directed the expansion of flame tree planting across streets, homes, recreational spaces, and public parks in Dubai.
The General Civil Aviation Authority (GCAA) has announced the full resumption of normal air navigation operations within UAE airspace and the lifting of temporary precautionary measures.
The UAE has welcomed a new resolution adopted by the International Maritime Organization’s (IMO) Marine Environment Protection Committee during its 84th session.
