French President Emmanuel Macron has called a snap parliamentary election, after the far-right National Rally won the European election in France
Mayor of Paris Anne Hidalgo says she's "stunned" by the decision to call the vote so close to the Olympic Games
The election will take place on 30 June and 7 July - the Games start in Paris on 26 July
In the election, the National Rally won more than double the votes of Macron's centrist alliance
Elsewhere in the European elections, European Commission chief Ursula von der Leyen said "the centre is holding"
But far-right parties made gains in Italy, Austria and Germany
In other election news, an Italian under house arrest in Hungary has been elected as an MEP, as has a 24-year-old YouTube prankster in Cyprus
Image source, ARIS MESSINIS/AFPIn short: Less than they used to.
Turnout was highest in 1979, when the first elections were held. In that year, it hit 61,99%.
It has been dwindling since, hitting a low of 42,61% in 2015. But it rebounded to 50.66% in 2019.
Turnout in the UK at the 2019 European election - the last the UK was eligible to take part in before Brexit - was around 35%, but that was because most voters saw little point.
Some countries try to attract voters - and cut on costs - by holding local elections on the same day. This year, that is the case in Hungary, Ireland and Italy.
Belgians are holding three. As well as the European election, they've got national and regional votes too.
Paul Kirby
Europe digital editor in Brussels
Image source, ReutersThis dog joined its owner at a polling booth in Budapest
Although 21 countries have been going to the polls today across the EU, polling stations opened in the Netherlands on Thursday, and opened in Ireland and the Czech Republic on Friday.
That’s because every EU country is allowed to choose which day to vote, between 6-9 June, and the Dutch, for example, don’t vote at weekends.
Czech voters had two days to go and vote, as Italians have had today and yesterday.
But it’s Estonia that’s given its voters the biggest window for casting their ballots.
Online voting began on Monday and closed yesterday, with more than 26% of Estonians choosing that way to vote.
But polling stations have also been open today, and if you didn’t like your online vote you can go and change your mind in person.
Image source, EPAThis child in Lisbon took a very active role in helping his dad vote
Even though these are not national elections, voters often use the European elections to send a message to their national governments.
That's why in from France to Germany, Austria to Belgium and beyond, parties on the far right are eyeing significant gains.
The centre right is widely expected to remain the biggest group in the European Parliament, but all eyes are on who comes second and third.
Polls ahead of the elections suggested Europe's two main right-wing political groups, ECR and ID, could overtake the centre left and become the second largest force in Parliament.
If that were to happen, the centre right could come under pressure to find new allies.
A move to the right could put the brakes on plans for new climate and sustainability laws and influence social or economic legislation.
The EU's strong backing for financial and military aid for Ukraine could also be affected.
Paul Kirby
Europe digital editor in Brussels
Voting has been taking place in 21 European countries today and won’t finish until the polls close in Italy at 23:00 - that’s 22:00 UK time.
And that’s when we’ll get the first results from across Europe. But we’ll be getting exit polls and projections far earlier than that.
I’m at the European Parliament where the first estimates will come through at around 17:15 UK time.
Voting will have just ended in Germany, which has the EU’s biggest national population and therefore most seats in Parliament, so that will be one of the first exit polls to look out for.
The Netherlands, Slovakia, the Czech Republic, Ireland, Malta and Latvia all finished voting before today.
More estimates will come through in the early evening until the first projections some time after 20:00 UK time, and they’re based on real vote samples.
Image source, OSCAR OLSSON/TT NEWS AGENCY/AFPSweden's opposition Social Democrat leader Magdalena Andersson voting in Stockholm today
At stake this weekend is the make-up of the next European Parliament, the direct link between Europeans and the EU's institutions.
So Europeans in 27 countries are choosing who will represent them in Brussels and Strasbourg, the two locations where the Parliament sits. There will be 720 MEPs in the next Parliament, and each country has a number in line with the size of its population.
They will pass laws that affect the lives of every EU citizen and they have to endorse the EU's annual budget, which this year reached €189bn(£160bn). The Parliament shares that power with the Council, made up the EU's national governments.
The next Parliament will shape the direction of the EU over the next five years, on climate change and migration, greater integration or increased nationalism.
Laura Gozzi
Europe reporter in Rome
Good afternoon from a sweltering Rome - and welcome to our live coverage of the fourth and final day of the European elections.
Over the last week, European voters in 27 nations have been called to cast their votes to elect the new 720 Members of the European Parliament. Just today, 21 countries are holding EU elections.
Will the right make big gains - or will the centre hold? We'll find out a bit later.
Estimates should start coming in from around 17:00 BST, and we're expecting the first projection of the new Parliament at around 19:00 BST.
We'll bring you all the latest news, colour and analysis from across Europe right on this page.