Leaders of three political parties will join tens of thousands of people opposed to the renewal of the Trident nuclear system in the biggest demonstration of its kind in a generation.
Labour leader Jeremy Corbyn, SNP's Nicola Sturgeon and Leanne Wood of Plaid Cymru will be among the speakers addressing a rally in central London today.
Union officials, faith leaders, anti-nuclear activists and anti-war campaigners will also take part in the Stop Trident protest.
Coaches will travel to the capital from across the UK, including Scotland, where the Trident submarines are based.
Organisers of the march said it will send a strong message of growing support against renewing the nuclear weapons system.
They also argued that worries about job losses were a "red herring", despite a warning by the GMB union this week that tens of thousands of jobs depended on the system's renewal.
Campaign for Nuclear Disarmament chair Kate Hudson said: "The extent of popular opposition is becoming clear. This will not be a gathering of the anti-nuclear clan - it will show the breadth of opposition."
Leanne Wood will say that nuclear weapons should be thrown into the "dustbin of history", adding: "When food bank use is at a record high, when the gap between the richest and the poorest is at its widest, when our NHS needs ever-greater investment, it is a disgrace that £100 billion and more will be diverted to nuclear weapons that no one should want and no one should ever use.
"This issue is bigger than any one political party. It is bigger than any one government and it is bigger than any one country.
"Just as war is a human-made construct, so too are weapons of mass destruction. It is the will of humanity that will secure their abolition."
Actress Vanessa Redgrave, Enter Shakiri's Rou Reynolds and comedienne Francesca Martinez will also address the rally.
The shadow cabinet has yet to decide how it will handle any Commons vote on Trident, expected later this year, ahead of the recommendations of a review of the party's existing support of renewal led by unilateralist shadow defence secretary Emily Thornberry.
Defence minister Philip Dunne said: "Thirty years ago, the leader of the opposition backed unilateral disarmament as we faced aggression from nuclear armed powers who did not share our values of democracy, freedom and the rule of law.
"Today, the picture is depressingly similar. Disarming now would be a reckless gamble with our national security that would play into the hands of our enemies."