First estimates gave 33 per cent of the vote in Flanders to the New Flemish Alliance (N-VA) headed by tough-talking Antwerp mayor Bart De Wever.
With Flanders in the north accounting for 60 percent of Belgium's population of 11 million, the result, if confirmed, would see the NV-A become the biggest party in the language-divided nation.
"Vicit vim virtus", De Wever told supporters in Latin -- meaning "Courage overcame violence".
The French-speaking Socialists from southern Wallonia, headed by incumbent premier Elio Di Rupo, scored just over 30 per cent.
However, De Wever's lead may prove to be too small to enable him to form a regional government in northern Flanders, while at the federal level he may find it difficult to find allies to join a coalition.
Belgium has no national political parties, with the current federal coalition government made up of groups from both sides of its invisible but very real linguistic border.
According to tradition, it will be up to King Philip to ask the leader of today's winning party to form a government.
It will his first election as king, having come to the throne only last year.
All eyes were on the N-VA showing in the election, the first since an inconclusive 2010 ballot left the divided country without a government for a world record 541 days.
The 2010-2011 deadlock was largely due to the N-VA's refusal to agree a coalition deal with other parties because of its demands for more devolution -- and ultimately its wish to separate Flanders from the rest of Belgium.
This time around De Wever, who was hugely acclaimed by supporters, said "we don't want a long political crisis ... we want to take the initiative to see what is possible."