Addressing flag-waving supporters late today, Orban said the result gave Hungarians "the opportunity to defend themselves and to defend Hungary".
The crowd cheered as a giant TV screen showed electoral maps of the country almost completely covered in Fidesz's orange colour.
At end of his speech, Orban led the crowd in singing a song from the country's 1848 revolution, "Long Live Hungarian Freedom".
One supporter, 53-year-old Eva Halasz, said: "Viktor is the only leader for Hungary, this proves he has the nation behind him, there is no-one in this country like him, there is no opposition here."
The surge in voter turnout was thought to likely favour the opposition Jobbik, a far-right party that has been moving towards the centre, and the centre-left Socialists.
However, with nearly all votes counted, results show Jobbik trailing far behind with 19.78 per cent, the Socialists on 12.35 per cent and the environmentalist LMP party on 6.89 per cent.
Jobbik's leader Gabor Vona may even fail to win the seat he contested in the northeastern town of Gyoengyoes.
Orban will likely seize on the results as vindication of his clashes with EU institutions over his hardline anti-immigration policies and rejection of the EU's refugee resettlement programme, as well as his moves to clamp down on civil society groups.
An Orban victory will also provide a fillip for other nationalist politicians and those on the far-right around Europe who look to him as an inspiration.
France's far-right leader Marine Le Pen tweeted her congratulations, saying the "mass immigration promoted by the EU has been rejected once again"..
Fidesz may even be on track to win its coveted two-thirds "supermajority" in parliament, which would grant it wide powers to press ahead with controversial measures and change the constitution
Some of the previous measures passed using this mechanism include those that have put Orban on a collision course with Brussels.
They include what critics call the erosion of media and judicial independence, as well as its crackdown on civil society organisations linked to liberal US billionaire George Soros.
Orban accuses Soros and the organisations he funds of promoting mass Muslim and African immigration into Europe in order to undermine its Christian identity.
The last few weeks of the campaign were marked by allegations of money laundering and corruption levelled at Orban's inner circle, often published in media owned by oligarch Lajos Simicska, an erstwhile Orban ally who fell out with him after Fidesz's 2014 election victory.
Orban avoided public debates with opponents or speaking to independent media, preferring instead to address supporters at carefully stage-managed events where he hammered home his anti-immigration message.
The opposition's campaign had focused on corruption and deteriorating public services, as well as the government's failure to stem a high level of emigration which has seen the country's population fall under the symbolic 10 million mark.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)