Taking the baton from Asia, where unions demanded wage increases as they transformed the day from one celebrating workers rights to one of international protest, workers turned out in droves in Greece, France and Spain, the latest focus of a debt nightmare that has already forced three eurozone countries to seek financial bailouts.
Under a gray, threatening Madrid sky that reflected the national mood, 25-year Adriana Jaime confided she turned out because she speaks three foreign languages and has a masters degree as a translator, but works for what she derided as peanuts and sees her future as grim at best.
"I am here because there is no future for the young people of this country," she said as marchers walked up the city's main north-south boulevard, protesting health care and education spending cuts and other austerity measures taken by the new conservative government. Many carried black and white placards, with the word NO and a pair of red scissors pictured inside the O.
Spanish Prime Minister Mariano Rajoy is trying desperately to cut a bloated deficit, restore investor confidence in Spain's public finances, lower the 24.4 jobless rate, and fend off fears it will join Greece, Ireland and Portugal in needing a bailout.
Ana Lopez, a 44-year-old civil servant, said May Day is sacred for her but this year in particular, arguing the government is doing nothing to help workers and that the economic crisis is benefiting banks.
"Money does not just disappear. It does not fly away. It just changes hands, and now it is with the banks," Lopez said. "And the politicians are puppets of the banks."
In France, tens of thousands of workers, leftists and union leaders were marking May Day with marches and rallies, in an optimistic mood ahead of presidential elections Sunday that a Socialist is expected to win for the first time since 1988.
Anger has emerged during the campaign at austerity measures pushed by European Union leaders and conservative President Nicolas Sarkozy. Many voters fear Sarkozy will erode France's welfare and worker protections, and see him as too friendly with the rich. Challenger and poll favorite Francois Hollande has promised high taxes on the rich.
In debt-crippled Greece, more than 2,000 people marched through central Athens in subdued May Day protests centered on the country's harsh austerity. Minor scuffles broke out in Athens when young men targeted political party stands, destroying two and partially burning another. There were no injuries.
In the United States, demonstrations, strikes and acts of civil disobedience were planned, including what could be the country's most high-profile Occupy rallies since the anti-Wall Street encampments came down in the fall.
Around 100,000 people in Moscow - including President Dmitry Medvedev and President-elect Vladimir Putin - took part in the main May Day march through the city center - though not to protest the government.
Television images showed the two leaders happily chatting with participants on the clear-and-cool spring day. Many banners and placards criticized the Russian opposition movement that has become more prominent in Moscow over the past half-year.
One read "spring has come, the swamp has dried up," referring to Bolotnaya (Swampy) Square, the site of some of the largest opposition demonstrations in recent months.
Earlier, thousands of workers protested in the Philippines, Indonesia, Taiwan and other Asian nations, with demands for wage hikes amid soaring oil prices a common theme. They said their take-home pay could not keep up with rising consumer prices, while also calling for lower school fees and expressing a variety of other complaints.
In the Philippine capital, Manila, more than 8,000 members of a huge labor alliance, many clad in red shirts and waving red streamers, marched under a brutal sun for 4 kilometers (2.5 miles) to a heavily barricaded bridge near the Malacanang presidential palace, which teemed with thousands of riot police, Manila police chief Alex Gutierrez said.
Another group of left-wing workers later burned a huge effigy of President Benigno Aquino III, depicting him as a lackey of the United States and big business. A few hundred workers marched to the U.S. Embassy, but were stopped by riot police about a block away. The protesters burned a mock U.S. flag and went away.
Aquino rejected their calls for a $3 daily pay hike, which he warned could worsen inflation, spark layoffs and turn away foreign investors.
Aside from pay hikes, protest leader Josua Mata from the Alliance of Progressive Labor urged Aquino to back proposed legislation against the widespread practices by businesses of contracting out some operations to other companies to save on costs and prevent workers from organizing trade unions.
In Indonesia, thousands of protesters demanding higher wages paraded through traffic-clogged streets in the capital, Jakarta, where 16,000 police and soldiers were deployed at locations including the presidential palace and airports.
There were also protests in Taiwan, Malaysia and Hong Kong.