Netumbo Nandi-Ndaitwah, from the governing South West Africa People's Organisation (Swapo), has been voted in as Namibia's first female president after last week's disputed election.
The electoral commission said she had won more than 57% of the votes cast, with her closest rival Panduleni Itula getting 26%.
But following logistical problems and a three-day extension to polling in some parts of the country, Itula said on Saturday that his party would not recognise the results alleging electoral malpractice.
As a consequence, most of the opposition parties boycotted the results announcement on Tuesday evening in the capital, Windhoek, The Namibian newspaper reports. "The Namibian nation has voted for peace and stability," the Reuters news agency quotes Nandi-Ndaitwah as saying once the outcome had been announced.