"I did not hear any dissenting voices," John Nkomo, the Zanu-PF chairman said, according to the French news agency.
"It means this congress has fully and unreservedly declared Comrade Robert Gabriel Mugabe as the presidential candidate for next year's presidential elections."
Reuters news agency reported that the announcement was greeted with cheers.
"Every one of them matters to me. Can I let them down?" AP news agency quotes Mr Mugabe as saying during his keynote address to delegates before his endorsement.
"No. Their welfare is my welfare. Their suffering is my suffering. I dare not abandon them," he said.
South Africa has been mediating talks between Mr Mugabe's government and the opposition Movement for Democratic Change (MDC) to prepare for free and fair elections next year.
But last week a faction of the divided MDC said Zanu-PF was not sincere or committed to dialogue. And in a new report human rights organisation Amnesty International says the opposition continue to suffer beatings, torture and harassment.
_______________________ Iwo to ti GBO, to ti SHA, to ti EXPA,
You come dey come to the club come dey buga..
-- You wey don OLD, don FADE, don EXPA,
Come dey come to the club come dey 'buga'..
- Durella, in Reconfigurated