Another vote must now be held within 60 days
Kenya is to hold another presidential election after the previous poll was declared invalid by the country's supreme court.
Judges ruled by a majority of 4-2 that the win by President Uhuru Kenyatta was "null and void" as a result of irregularities committed by the election board and ordered a fresh ballot be held within 60 days.
It is the first time in Kenya's history an election result has been cancelled.
The historic move comes after a petition was filed by opposition candidate Raila Odinga.
He had claimed the electronic voting results were hacked into and rigged in favour of Mr Kenyatta.
The Kenyan leader had won a second term on 8 August with 54% of the vote, but the court has now decided the poll was not conducted in line with the constitution.
Judge David Maranga, announcing the verdict, said: "The declaration (of Kenyatta's win) is invalid, null and void.
"The first respondent (the election board) failed neglected or refused to conduct the presidential election in a manner consistent with the dictates of the constitution."
Mr Odinga said: "This is a historic day for the people of Kenya and by extension for the people of the continent of Africa."
The court's decision paves the way for a new race for the presidency between Mr Kenyatta and Mr Odinga.
Kenya's main domestic poll monitoring organisation, ELOG, had previously said it found no evidence to suggest the election was manipulated or inaccurate.
Mr Odinga has contested the last three elections and lost each time.
On each occasion he has alleged the polls had been rigged.
In 2013, the supreme court dismissed his petition.
A number of people died last month after protests over the latest election result turned violent.