Trade unionists, anti-capitalists and public sector cuts protesters are set to stage a series of rallies across the UK to mark May Day.
Leaders of trade unions will address a rally in London's Trafalgar Square against a backdrop of disputes in the public sector over jobs, pay and pensions.
"Attacks on the NHS, education, pensions, the civil service, local government, jobs both public and private sector, the disabled and women mean we have to fight back and say there is a different way forward," one of the organisers said.
Tens of thousands of civil servants, lecturers, health workers, Ministry of Defence staff and Royal Fleet Auxiliary employees are also taking industrial action on 10 May in a bitter dispute over the government's controversial public sector reforms.
The Occupy movement, behind the Occupy LSX camp outside St Paul's Cathedral, are planning to 'Occupy the Tube' on May Day but details behind the protest have yet to be revealed.
Anti-tax avoidance protesters are also planning to target Tube stations as part of their demonstration plans.
Tuesday also marks 'National CC All Your Emails To Theresa May Day', which encourages anti-snooping law protesters to flood the Home Office's inbox with emails in response to plans to monitor the country's internet use.
May Day has been celebrated in London since the 1880s and the event in the capital will be supported by a wide variety of groups representing workers, students, pensioners and politicians.
Campaigners continue to call for May 1 to be a public holiday.
See the slideshow below for pictures of what's been happening across the world this May Day...