Up to 400 million Europeans are electing 751 MEPs to represent them in Brussels and Strasbourg over the next five years.
Despite the looming spectre of Brexit, the UK kicked off voting on Thursday. The Czech Republic, Latvia, Slovakia and Malta cast their ballots on Saturday, with the rest of the bloc heading to the polls on Sunday.
Most EU countries headed to the polls on Sunday: Austria, Belgium, Bulgaria, Croatia, Cyprus, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Lithuania, Luxembourg, Poland, Portugal, Romania, Slovenia, Spain and Sweden.
MEPs are elected to represent regions in some countries, like Italy, while in others, such as Germany, they have the whole country as their constituency.
Germany, the most populous, will get 96 MEPs for its 82.8 million people, while tiny Malta, with 475,000 people, has just six.
They pass EU laws and approve its budget, along with the European Council, which comprises of the heads of state of each country.
MEPs represent individual countries or regions but in parliament sit in transnational groups according to political ideology.
For example, there are groupings to represent the centre-right, socialists, greens and others for eurosceptics.
MEPs also help choose the president of the European Commission, the EU’s civil service.
The largest political grouping after May’s election has the strongest mandate to have its choice head up the commission.
Last time around that was the European People’s Party, who managed to get its candidate, Jean-Claude Juncker, into the hot seat.
To appoint the commission president, another body, the European Council, comprising chiefs of EU countries, first votes on a nominee chosen after taking into account the election result.
If they approve the candidate, it goes to the European Parliament, where he or she must get the support of a majority of MEPs.
Only then does he or she become president of the European Commission.