The movement's website showed which areas of Europe were most enthusiastic: Germany held over 900 events, France over 600, and Italy over 500.
Around 50 million volunteers in 180 countries have picked up litter beside rivers, on beaches, and in forests on World Cleanup Day.
Each year eight million tons of plastic end up in the oceans, which are also where 70 per cent of the world's oxygen is generated.
In Rome, on Saturday dozens of volunteers filled up bags with seemingly endless amounts of rubbish along the river Tiber.
"We were raised that way," one of the young volunteers said. "We see with climate change and global warming, it's all kind going down south, So I think it's time #we all get engaged to start the real action."
"The old people can make policies, we will do action," said one volunteer as she filled up another bag.
In Sarajevo, the capital of Bosnia, volunteers cleaned up promenades and parks across the city on Saturday.
They also picked up litter on the slopes of Mount Trebevic, which overlook the capital and were used for several events during the 1984 Winter Olympics.
World Cleanup Day's website reveals which areas of Europe were most enthusiastic on Saturday: Germany came top of the list, holding more than 900 registered events, France more than 600, and Italy more than 500.
But the website also revealed that people in Cyprus, Latvia, Liechtenstein, Moldova, Romania, Slovenia, and Ukraine didn't register any events at all.
In other parts of the world, there was even more at stake. in South Africa, like the river Tiber, the banks of the Jukskei river are strewn with rubbish.
It runs through the impoverished township of Alexandra in South Africa's economic capital, Johannesburg.
But the sewage-stricken river also has to be a source of drinking water for people who still haven't been provided with piped water in their homes.
Volunteers' bags filled up fast on Saturday. Local organisers said their ultimate aim was to persuade to residents that it's possible to clean the river up well enough that it's safe to drink from.