Biya's re-election comes amid claims from the opposition of electoral fraud that included ballot stuffing and voter intimidation.
Cameroonian President Paul Biya won an emphatic election victory with 71 percent of the vote, the Constitutional Council announced on Monday, extending his 36-year rule and cementing his place as one of Africa's longest-standing rulers.
The widely-expected win gives the 85-year-old a seventh term in office and could see him in power until at least the age of 92. The only current African president to have ruled longer is Equatorial Guinea's Teodoro Obiang Nguema Mbasogo.
Most Cameroonians have known just one president.
Victory in the October 7 poll came amid claims from opposition candidates that the election was marred by fraud, including ballot stuffing and voter intimidation. The Constitutional Council rejected all 18 petitions claiming fraud last week.
In addition, violence connected to a separatist movement in the western Anglophone regions forced tens of thousands to flee in the run-up to the vote and kept the vast majority there from casting their ballot.
The announcement follows two weeks of political tension in the coffee and oil-producing country, during which Biya's leading rival Maurice Kamto claimed victory based on his campaign's figures, and as police tried to silence opposition marches in the port city of Douala.
Monday's official results showed Kamto won 14 percent of the vote. Biya won with a big margin in nine of the 10 regions. In the south and east regions he won over 90 percent of the vote.
Authorities have defended the process. "The election was free, fair and credible in spite of the security challenges in the English-speaking regions," said the President of the Constitutional Council, Clement Atangana, on Monday.