Election victor Péter Magyar, a former Orbán loyalist who campaigned against corruption and on everyday issues like health care and public transport, has pledged to rebuild Hungary's relationships with the European Union and NATO — ties that frayed under Orbán.
European leaders quickly congratulated Magyar.
It's not yet clear whether Magyar's Tisza party will have the two-thirds majority in parliament to govern without a coalition.
With 77 per cent of the vote counted, it had more than 53 per cent support to 38 per cent for Orbán's governing Fidesz party.
It's a stunning blow for Orbán, a close ally of both US President Donald Trump and Russian President Vladimir Putin. Orbán conceded defeat after what he called a "painful" election result.
"I congratulated the victorious party," Orban told followers.
"We are going to serve the Hungarian nation and our homeland from opposition," he said.
''Thank you, Hungary!" Magyar posted on X, as thousands of his supporters thronged the banks of the Danube in Budapest, chanting "We got it! We did it!"
Orbán, the EU's longest-serving leader and one of its biggest antagonists, who has travelled a long road from his early days as a liberal, anti-Soviet firebrand to the Russia-friendly nationalist admired today by the global far-right.
Turnout by 6:30pm was over 77 per cent, according to the National Election Office, a record number in any election in Hungary's post-Communist history.
The parties of both Orbán and Magyar said they had received reports of electoral violations, suggesting some results could be disputed by both sides.
"I'm asking our supporters and all Hungarians: Let's stay peaceful, cheerful, and if the results confirm our expectations, let's throw a big, Hungarian carnival," Magyar said.
Mark Radnai, Tisza's vice president, also called for reconciliation after a tense campaign.
"We can't be each other's enemies. Reach out, hug your neighbours, your relatives. It's the day of reunification."
The EU will be waiting to see what Magyar does about Ukraine.
Orbán repeatedly frustrated EU efforts to support Ukraine in its war against Russia's full-scale invasion, while cultivating close ties to Putin and refusing to end Hungary's dependence on Russian energy imports.
Recent revelations have shown a top member of Orban's government frequently shared the contents of EU discussions with Moscow, raising accusations that Hungary was acting on Russia's behalf within the bloc.
Orbán occupied an outsized role in far-right populist politics worldwide.
Members of Trump's "Make America Great Again" movement are among those who see Orbán's government and his Fidesz political party as shining examples of conservative, anti-globalist politics in action, while he is reviled by advocates of liberal democracy and the rule of law.
Casting his ballot in Budapest, Marcell Mehringer, 21, said he was voting "primarily so that Hungary will finally be a so-called European country, and so that young people, and really everyone, will do their fundamental civic duty to unite this nation a bit and to break down these boundaries borne of hatred".
During his 16 years as prime minister, Orbán launched harsh crackdowns on minority rights and media freedoms, subverted many of Hungary's institutions and was accused of siphoning large sums of money into the coffers of his allied business elite, an allegation he denies.
He also heavily strained Hungary's relationship with the EU.
Although Hungary is one of the smaller EU countries, with a population of 9.5 million, Orbán has repeatedly used his veto to block decisions that require unanimity.
Most recently, he blocked a 90-billion euro ($104 billion) EU loan to Ukraine, prompting his partners to accuse him of hijacking the critical aid.
