The constitutional court in the Democratic Republic of the Congo confirmed the victory of the presidential candidate Felix Tshisekedi.
The court rejected an appeal by Martin Fayulu, another opposition contender in the December 30th poll.
Fayulu claimed that Mr. Tshisekedi had entered into a power-sharing agreement with outgoing President Joseph Kabila. Mr. Tshisekedi's team denies it.
Despite the court's ruling, Fayulu said he was a "legitimate" president.
The African Union (AU) said today that there are "serious doubts" about the election result.
What did the court say?
The court said that Fayulu failed to prove that the electoral commission had announced false results.
He continued by declaring "Felix Tshisekedi president of the Democratic Republic of Congo with a simple majority".
It is now expected that you take an oath within 10 days.
The confirmation of the official result creates the first transfer of power ordered by the independence of the Democratic Republic of the Congo from 1960 to 1960.
The electoral commission announced earlier that Tshisekedi had received 38.5% of the votes, compared to 34.7% of Mr. Fayulu.
The candidate for the Emmanuel Shadary coalition took 23.8%.
However, Mr. Fayulu had claimed that Mr. Tshisekedi had made an agreement with Kabila, who has been in office for 18 years.
After the sentence, Fayulu urged the international community not to recognize the election result.
What did the others say?
The official figures have been challenged by the influential Catholic Church which claims to have deployed 40,000 election observers across the country.
Even international experts based in the United States and French and German governments have raised doubts.
Meanwhile, the UN says ethnic violence in the west of the country has killed at least 890 people in just three days last month.
Clashes between the communities of Banunu and Batende took place in four villages in the Yumbi area between 16 and 18 December, according to the UN Office of Human Rights.
The vote in the presidential elections was postponed to Yumbi because of violence.
Most of the population of the area was displaced, including about 16,000 people who sought refuge crossing the Congo River in the neighboring Republic of the Congo, also known as Congo-Brazzaville.
About 465 homes and buildings have been burned or looted, including two primary schools, a health center and the office of the Independent Electoral Commission, the United Nations reported.