The endorsement, which is likely to result in his 36-year rule being extended, was greeted with thunderous applause by thousands of party faithful.
The endorsement, which is likely to result in his 36-year rule being extended, was greeted with thunderous applause by thousands of party faithful attending the ruling ZANU-PF's annual conference.
Mugabe accepted dressed in a green floral jacket bearing his own portrait and a map of Zimbabwe.
The veteran leader has held power since independence from British colonial rule in 1980 and has always avoided naming a successor or laying out plans to retire.
He once joked that he would rule until he turned 100.
The conference, held in the southeastern town of Masvingo, voiced "its support to the president and first secretary comrade Robert Mugabe as the sole candidate for the forthcoming 2018 elections", deputy secretary Eunice Sandi Moyo said.
The absence of a clear successor to Mugabe has sparked infighting including verbal exchanges on social media in recent weeks between factions angling for his position.
Accepting his endorsement, Mugabe called for unity among party supporters.
"We agreed that conflicts should end. Infighting should end. The party ideology should be followed," he said.
Mugabe, who has been dogged by rumours of poor health and is usually animated during lengthy political addresses, spoke slowly during his short acceptance speech.
He stressed that discipline among party members should be maintained and that "leaders should be respected".
"Let us be one. We are one family, the family of ZANU-PF bound together by the fact of understanding between its members," he said.
Large portraits of a younger Mugabe hung around a huge marquee where the conference was held, with the majority of the around 9,000 delegates donning shirts emblazoned with their leader's face.
"We want President Mugabe to rule forever and ever because of his clear leadership," one elated delegate, Janet Mazviwanza, told AFP.
Despite his popularity within the party ranks, Mugabe this year faced unprecedented calls for him to step down, including a series of rare public protests over his failure to turn the ailing economy around.
Critical cash shortages prompted the government at the end of November to introduce the much disliked 'bond notes" -- equivalent to the US dollar.
Unemployment in the country is currently at about 90 percent, and thousands of companies have closed in the last three years.
Zimbabwe abandoned its own dollar currency in 2009 after hyperinflation hit 500 billion percent rendering it unusable.
Among the protest groups at rallies in recent months have been university graduates who wore their gowns and caps to show their anger at the lack of jobs.
The street protests led police to ban demonstrations in the capital Harare, with some activists arrested by the police.