On Sunday, European leaders approved Britain's departure from the 28-member EU bloc after more than 40 years of membership.
The two documents approved at the summit in Brussels were the legally binding 585-page withdrawal agreement and a political declaration. Between them, they set out the terms of the UK leaving the bloc and the future relationship between both sides.
The UK is scheduled to leave the EU on 29 March 2019.
The next step is for May to try and get MPs to back the deal, with most currently standing against it. MPs are set to vote on the divorce deal with the European Union before Christmas.
The main sticking point ahead of Sunday's summit had been the issue of Gibraltar. However, a last-minute fix was found.
Yet Northern Ireland DUP leader Arlene Foster said Saturday she would vote against the deal if the Irish backstop is not removed from the agreement, fearing a separate customs arrangement between Northern Ireland and mainland Britain could lead to the breakup of the UK.
The 'best and only deal' says May and Juncker
After the summit, May said her Brexit accord was the best possible deal and it unlocked a bright future for the UK, adding that its acceptance marked the start of a crucial national debate.
The PM, however, avoided answering questions on whether she will resign if the deal is rejected by the House of Commons.
May also said there would be no second referendum and that it's time for the country to move on, adding that she's "full of optimism" that the UK and EU will remain good friends and neighbours.
On Saturday, May released a letter to the nation asking Britons to back her deal.
EU Commission President Jean-Claude Juncker said it was the 'only deal' and warn Britons a better one will not follow.
"I invite those who have to ratify it in the UK House of Commons to do so," he added.
Reactions from EU leaders:
EU commission president Jean-Claude Juncker
“It is a sad day. Seeing a country like Great Britain, but I would say this of any others, leaving the European Union is not a moment of jubilation or celebration. It is a sad moment, a tragedy.
“I would vote in favour of this deal because this is the best deal possible for Britain ... and the European Union will not change its fundamental position when it comes to this issue.”
European Parliament President Antonio Tajani
“Today is not a good day.
“The European Parliament will stress its role (referring to any extension of the transition period) ... Changes cannot be made without the due involvement of the European Parliament.”
EU Chief Brexit Negotiator Michel Barnier
"We have negotiated with the UK, never against the UK. Now it is time for everybody to take their responsibility, everybody.
"This deal is a necessary step to build trust between the UK and the EU that we need for the next phase of this unprecedented and ambitious partnership. We will remain allies, partners and friends.”
French president Emmanuel Macron
"This is a summit of unity and of gravity," he said. "The Brexit is far from over, there are a few steps left."
German Chancellor Angela Merkel
"We want a close cooperation with the UK," Merkel said. "As May said, UK is leaving EU and not Europe."
On the prospect of the deal being rejected by UK parliament:
“This is a speculative question that I cannot answer. We have committed to something in a very difficult situation and I think that Theresa May, as British prime minister, will do everything she can to play her part and so we are concentrating on completing the course we have set ourselves on.”
Spanish prime minister Pedro Sanchez
'Today is a sad day for Europe and all Europeans,' Sanchez said, adding that as "a convinced European" he was "satisfied" with the deal.
In relation to Gibraltar; he added: "We are sat in a strong position that we never had before."
Dutch Prime Minister Mark Rutte
“This is a balanced outcome with no political winners or victories, but I think it is acceptable.
“I don’t want to contemplate a no vote. I think there will be a yes vote, but more in general, I think this is the maximum we can all do, both Theresa May and her government as well as the European Union. No victors here today, nobody winning, we’re all losing, but given the context, that is acceptable.”
Follow our live updates here: