The party's nomination was expected.
In January, a super-legislature stacked with Maduro loyalists announced that the presidential election, originally scheduled for December, was being brought forward by months.
The Supreme Court, which critics say systematically bows to Maduro, then barred the opposition coalition from fielding a candidate under its banner, and banned several prominent figures from participating.
The opposition, which is fractured and weakened, said the moves are designed to engineer a second term for Maduro, who is broadly unpopular but faces no single opposition figure with strong support.
Maduro, dressed in the color red adopted by the Socialist Party and accompanied by his wife Cilia Flores, accepted the nomination as hundreds of party members yelled "Yes."
Cabello said it was "totally natural" that Maduro, 55, be given the nomination, calling him a "comrade of irreproachable revolutionary conduct."
"We are going to win, I have no doubts of that," Cabello said.
The election will be held against a backdrop of financial and political crisis.
The country, impoverished despite being a major oil producer, is suffering food and medicine shortages brought on by a recent period of low oil prices, declining production, and economic mismanagement. It also is in the grips of hyperinflation and is teetering on the brink of outright default.
Venezuela is also increasingly isolated internationally.
The US and EU have imposed sanctions on Maduro and his officials, with Washington calling him a "dictator."
Argentina has said it will not recognize the results of the presidential election, and other major South American nations may follow suit.
US Secretary of State Rex Tillerson is touring South America during which he is raising Venezuela's crisis with governments in the region.
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