MPs, actors and thousands of demonstrators are expected to join in a march urging the Government to take more action on the refugee crisis.
They will begin in London's Park Lane at 12.30pm on Saturday before marching under a "Refugees Welcome" banner to a rally in Parliament Square.
Actors Vanessa Redgrave, Douglas Booth and Juliet Stevenson are set to join them, with some giving speeches at the rally from 3pm.
Green Party co-leader Caroline Lucas MP, Labour's Lord Alf Dubs and Liberal Democrat campaigner Baroness Sheehan will also speak.
According to organisers Solidarity with Refugees, last year's event attracted 100,000 demonstrators, shortly following the publication of an image of refugee toddler Alan Kurdi's body washed up on a beach in Turkey.
The group said that at least 50 organisations and 200 religious leaders are involved in this year's rally and have together written to the Government demanding that the UK take a "fair and proportionate" share of international refugees.
The letter urged authorities to provide more safe routes of passage to the UK and offer more support to those already in the country, on top of the UK's current commitment to resettle 20,000 Syrians by 2020.
These demands come days before Prime Minister Theresa May is set to attend US summits discussing international responses to the refugee crisis.
Solidarity with Refugees director Ros Ereira said: "The summits next week in the US are the best opportunity for our Government to take proper action to tackle the refugee crisis, committing Britain to taking its fair share of responsibility.
"And this demonstration is the public's best opportunity to show the Government that's what we want them to do. Britain is a country that should welcome people fleeing desperate situations - let's make that message heard loud and clear."
Truly, Madly, Deeply actress Juliet Stevenson, who is currently starring in BBC thriller One of Us, added: "This march will unify people from all backgrounds and creeds under a single banner - that refugees are welcome here in Britain.
"The global refugee crisis is worse than ever, so now is not the time for us to stand idly by. The Government must take urgent action now or history may judge us very harshly."
The rally will also hear from refugees who have joined the campaign after finding a safe home in the UK.
Freshta Sharif, whose family fled Afghanistan in 1993, said: "As a refugee I know how important it is for countries to welcome and offer sanctuary to people fleeing violence and persecution.
"If it wasn't for the UK granting asylum to my family after it got too dangerous for us to stay in Afghanistan, I might not be here today.
"We're in the middle of a massive refugee crisis and I would like to see UK politicians commit to throwing the same lifeline to far more people who need it."
According to the UN's refugee agency, more than 3,200 people have died or gone missing attempting to cross the Mediterranean to Europe so far this year.
Figures show a total of almost 300,000 people have attempted the journey and thousands remain stranded in Greece and Italy in poor living conditions.