More than 200 million citizens across the 28-nation bloc cast their votes on Sunday for 751 EU parliament seats, with Eurosceptic forces making strong gains.
Eurosceptic parties hoped to capture as many as a third of the seats in the EU parliament, disrupting Brussels' pro-integration consensus.
French far-right leader Marine Le Pen won her symbolic duel with President Emmanuel Macron. Lead campaigner for her National Rally party, Jordan Bardella, said: “The gains for our allies in Europe and the emergence of new forces across the continent... open the way for the formation of a powerful group."
"The French have made their voices heard...and have given the president a lesson in humility"
Aujourd'hui, le peuple français a fait entendre sa voix et a infligé une sanction claire et une leçon d'humilité au Président de la République.Jordan Bardella (@J_Bardella) May 26, 2019
C'est une satisfaction immense pour tous ceux qui n'ont jamais cessé de croire en la FRANCE !#LaVictoireDuPeuple pic.twitter.com/Z92bTSiOCA
In Italy, exit polls showed the far-right League of Interior Minster Matteo Salvini with 27 to 31 percent of the vote. The party was significantly ahead of coalition partners in the anti-establishment Five Star Movement, which was neck-and-neck with the centre-left Democratic Party
Belgium's far-right Flemish nationalist Vlaams Belang party made strong gains in European elections, as well as national and regional polls also held on Sunday.
In Hungary, nationalist Prime Minister Viktor Orban's Fidesz party looked set for a big win, with polls giving it around 56 percent of the vote.
Poland's ruling right-wing Law and Justice party (PiS) took 42.4 percent to edge the opposition liberal coalition.
Early results from the UK vote gave a strong lead to the Brexit party of leading Leave campaigner, Nigel Farage.
The British elections come amid the prolonged uncertainty of Brexit – even if the UK does finally leave the EU on 31 October, the latest date set for its departure, its MEPs could still play a key role in the summer scramble to hand out top jobs at EU parliament.
But far-right parties have not had everything go their way.
Greens gain in Germany
In Germany, exit polls show Chancellor Angela Merkel's centre-right CDU maintaining the largest vote share, despite an historic low result of 28 percent, sharply down from 35.4 percent in 2014.
The far-right Alternative for Germany took 10.5 percent, better than 2014 but less than its result in national polls in 2017.
The big winners in Germany were the Greens, with the largest share of seats in the EU parliament, doubling their score to 22 percent, in second place.
The centre-left Social Democrats fells to 15.5 percent from 27.3 percent in 2014.
In Austria, the centre-right People's Party of Chancellor Sebastian Kurz was on course to gain seats, with the Social Democrats in second and the far-right Freedom Party (FPOe) coming third.
The results follow a corruption scandal in the FPOe that led Kurz to dissolve his coalition with the far-right party and call early elections for the autumn.
Greece's Tsipras announces early election
In the Netherlands, the centre-left party of EU vice president Frans Timmermans emerged a surprise comeback winner to upset the populist Eurosceptic parties.
In Greece, Prime Minister Alexis Tsipras said he would call early elections after voters dealt a huge blow to his party, with exit polls giving the opposition conservative New Democracy party an eight-point lead.
In Spain, acting Prime Minister Pedro Sanchez was the big winner with his ruling Socialists taking the largest vote share, with close to 33 percent, followed by the conservative Popular Party with 20 percent.