The IOM says the million mark was crossed on Monday
More than one million migrants and refugees have entered Europe this year, according to an intergovernmental organisation.
The International Organization for Migration (IOM) says the million mark was crossed Monday - marking more than a four-fold increase in comparison with last year.
The Geneva-based group says says more than 800,000 crossed into Greece from Turkey, including more than 455,000 from Syria and over 186,000 from Afghanistan.
Nearly 3,700 others died trying to cross the Mediterranean amid Europe's worst refugee crisis since World War II, it added.
Germany has seen around one million migrants arrive this year, but that figure includes large numbers of people from Balkan countries who arrived earlier in 2015.
The vast majority of the arrivals from outside Europe have used the so-called Balkan corridor - a route that takes migrants from Greece, through Macedonia, Serbia, and then either Croatia and Slovenia or Hungary to Austria and Germany.
The UN refugee agency urged Hungary on Monday to end policies that promote "intolerance and hatred" after the country built a huge fence along its southern border to keep migrants out.
The Hungarian government launched a campaign earlier this month that the UNHCR said portrayed refugees, most of them coming from war-torn Syria, as "criminals, invaders and terrorists based on their religious beliefs and places of origin".
The IOM said anti-migrant sentiment taking hold in several nations facing an influx of refugees is disturbing, dangerous and puts people's lives at risk.
Its director-general, William Lacy Swing, said: "We're very disturbed at the widespread anti-migrant sentiment that can lead to xenophobia and risks to migrants.
"The concern I have about a lot of statements that are being made on the public record right now is that it puts migrant lives at risk".
"All of our countries have always been open to new influx of people and it's always benefited us".
The IOM says it has helped more than 3.6 million people in Syria with services including shelter, water and sanitation.
More than four million Syrians have sought refuge outside their country since civil war erupted in March 2011.
Others, who some categorise as economic migrants, have been coming to Europe in large numbers from Pakistan, Eritrea, Bangladesh and Nigeria.