Members of the European Parliament are bidding farewell to UK colleagues ahead of a final vote on the Brexit deal.
The withdrawal agreement is expected to be signed off in Brussels later.
Some MEPs have marked the occasion with songs - others wore "always united" scarves. President of the European Commission Ursula von der Leyen told the UK: "We will always love you."
But Eurosceptics, including the Brexit Party's Nigel Farage, used their speeches to tear into the EU.
The UK is due to leave the bloc at 23:00 GMT on Friday.
Ratification of the withdrawal agreement, agreed by the UK and EU in October, is not in doubt after it easily cleared its committee stage last week.
Departing British members are expected to be serenaded by their colleagues in a special ceremony after the vote, which is due at 17.00 GMT.
The session sees those on either side of the Brexit debate, including the UK's 73 MEPs, celebrate or lament the end of British EU membership.
The Parliament's Brexit spokesman, Guy Verhofstadt, said it was "sad to see a country leaving that has twice given its blood to liberate Europe".
He added that British MEPs had brought "wit, charm, and intelligence" as well as "stubbornness", and would be missed.
Mrs von der Leyen says ratification of the withdrawal deal was "only a first step" towards a new partnership between the EU and the UK.
She says the two should "join forces" in areas such as climate change, and seek a close partnership following the UK's exit on Friday.
The EU president finished her speech by saying: "We will always love you, and we will not be far. Long live Europe."
Conservative MEP and prominent Eurosceptic Daniel Hannan said opinion in Britain turned against the bloc when it became clear "the aspiration was to have the EU as a quasi-state".
"If at any stage Britain had been able to have a trade-only relationship that would have been enough," he went on, but added: "You are losing a bad tenant and gaining a good neighbour."
Mr Farage used his final speech to excoriate the EU, branding it "anti-democratic".
He has been campaigning for the UK's exit since before he was first elected to the Brussels Parliament in 1999.
"I want Brexit to start a debate right across Europe - what do we want from Europe?" Mr Farage said, arguing that "trade, friendship, co-operation and reciprocity" between nations could be achieved without "all of these institutions and all of this power".
He and his fellow Brexit Party MEPs waved Union flags before walking out of the chamber en masse.A tearful Molly Scott Cato was applauded and hugged by her colleagues after she spoke of her "grief and regret" at Brexit and the hope she would return to the European Parliament "one day".
"While now is not the time to campaign to rejoin the EU, we must keep the dream alive," the Green Party MEP said.
Belgian MEP Philippe Lamberts said the EU must learn lessons from the UK's decision to leave.
He said the bloc had to "regain the hearts and minds of European citizens" by focusing on what it could do for the many, not the few.
Earlier, the S&D coalition, which houses Labour's 10 MEPs, displayed a sign aimed at departing British members, which read: "It's not goodbye, it's au revoir."
European Parliament President David Sassoli, also a member of the group, joined the group in a rendition of Auld Lang Syne.
On Tuesday evening, several MEPs in the Green group also held a ceremony to mark the UK's departure.
While Brexit Party MEPs spoke of their joy and relief at leaving, others shared messages of sadness on social media as they prepared to vote for the last time.
Liberal Democrats shared pictures of gifts from the pro-European Renew Europe group.The Green Party's Alexandra Phillips tweeted: "I'm devastated to be leaving the best job in the world. I get to make real change every day while being surrounded by 27 different languages and cultures."The EU's negotiators have kept the European Parliament on board throughout the Brexit process.
Its main committees have given their approval. So it's inevitable that the deal will be endorsed. Instead of a moment of jeopardy, this is likely to be the highest profile event in the EU's distinctly low-key goodbye to the UK.
Expect speeches that praise EU unity and describe the UK's departure as a regrettable mistake. A German MEP is planning a sing-a-long to Auld Lang Syne. The SNP group have arranged for a piper to play them out of the building.
In the meantime, the 73 British members are packing their belongings into their regulation-issue 15 cardboard boxes.
The main send-off will happen on Friday, when the president of the European Parliament will deliver a joint statement alongside the presidents of the European Council and the European Commission.
The British flag that flutters outside the parliamentary premises will be lowered in the early hours of Saturday morning, before it's displayed in a museum.
After the UK leaves, there will be an 11-month transition period in which the two sides hope to negotiate their future economic relationship.
Trade talks are expected to begin in earnest in early March. The European Parliament will also get a say in ratifying any future trade deal.
The UK has insisted talks should not extend beyond 31 December 2020 when a transition period - which will see the UK follow EU rules - comes to an end.
President Sassoli told CNN on Tuesday that the timetable for a deal was tight.
He said the UK's exit would be "painful" for the bloc but building a new partnership based upon friendly co-operation and mutual interests was now essential.