Former French foreign minister Michel Barnier has been appointed to lead the European Union's negotiations with Britain over Brexit, reports BBC News.
Announcing the appointment, European Commission President Jean-Claude Juncker said he "wanted an experienced politician for this difficult job".
Mr Barnier will take up his post on October 1st.
A former EU commissioner, Mr Barnier led the EU's banking reforms - a move unpopular in London's finance district.
In a tweet, Mr Barnier said he was honoured to be appointed to the role.
Mr Barnier will work with his British opposite number, Brexit minister David Davis, who was at the forefront of the campaign to leave the EU.
Negotiations will only begin when Article 50 is triggered.
Mr Barnier is known as a tough negotiator.
As European commissioner for financial services between 2010 and 2014, he spearheaded the overhaul of EU banking laws in the aftermath of the 2008 financial crisis.
These included a swathe of measures, which included capping banker bonuses and a crackdown on short selling - some of which were objected to by the City of London.
Comments on social media by British political editors have already declared the appointment an 'act of war'.
The BBC's chief correspondent Gavin Hewitt points out that Mr Barnier will come with a French, as well as a Brussels, brief.
European Council President Donald Tusk, who chairs EU summits, had previously appointed Belgian EU official Didier Seeuws to oversee preparations for the Brexit negotiations.
It was not immediately clear what the relationship between Mr Barnier and Mr Seeuws would be.
Read more of this report from BBC News.