- The DRC has been in the grip of a two-year-old crisis over the succession of President Joseph Kabila, who said last year he would step down after nearly two decades in power.
- Congo's electoral commission said Mr Tshisekedi gained 38.57 per cent of the vote.
- The candidate Kabila hand-picked to succeed him, loyalist former interior minister Emmanuel Ramazani Shadary, came third in the poll.
- The other main opposition candidate, former oil executive Martin Fayulu came second, official results showed.
The Democratic Republic of Congo is set to see its first handover of power in 18 years after opposition candidate Felix Tshisekedi was Thursday named by election officials as the provisional winner of an historic presidential poll.
The election's supervisors had faced mounting pressure at home and abroad to publish the results after repeated delays stoked fears for the giant country's stability.
"Having gained... 38.57 percent of the vote, Felix Tshisekedi is provisionally declared the elected president of the Democratic Republic of Congo," said Corneille Nangaa, the head of the Independent National Election Commission (CENI).
Shouts of joy erupted at the commission's offices as the results were announced early Thursday morning, AFP journalists reported.
The DRC — a vast and poor country burdened by a history of bloodshed — has been in the grip of a two-year crisis over the succession of President Joseph Kabila, who said last year he would finally step down after nearly two decades as leader.
The mineral-rich country has never had a peaceful transition of power since it gained independence from Belgium in 1960.
The candidate Kabila hand-picked to succeed him, loyalist former interior minister Emmanuel Ramazani Shadary, came third in the poll.
The other main opposition candidate, former oil executive Martin Fayulu came second, official results showed.
The son of major Congolese political figure Etienne Tshisekedi, the 55-year-old president-elect is the head of country's long-time main opposition party UDPS.
According to the initial timetable set out by the CENI, the definitive results are due on January 15 with the swearing-in of the new president three days later.
As the lengthy results were read out on nationwide TV, police were deployed at strategic spots in the capital Kinshasa where, for the second evening running, many residents went home and locked their doors early.
Kabila, 47, was due to step down two years ago but clung to office, sparking widespread protests that were repressed at the cost of scores of lives.
The elections were held on December 30, but CENI last weekend said provisional results, expected on Sunday, would be held up because of logistical problems.
The long delay sparked blunt warnings from inside and outside the DRC, but also coincided with an apparent overture to Kabila from opposition leaders.
After deploying tens of thousands of its own election observers, the powerful Catholic Church last week said it knew the outcome of the ballot and called on the authorities to reveal the result "in keeping with truth and justice".
Campaign groups on Wednesday had called for the immediate release of the results and told people "to be prepared to go out onto the streets in massive numbers" if the outcome failed to accurately reflect the vote.
South Africa and Zambia, DRC's neighbour to the south, joined the clamour to publish the results.
"The delay in releasing the results of the elections can lead to suspicions and compromise peace and stability of the country," South African President Cyril Ramaphosa and Zambian counterpart Edgar Lungu said in a joint statement.