Since the vote and deadly anti-government protests which followed, Maduro's administration has conducted what the opposition, human rights groups and unions have characterised as a crackdown on dissent.
The actions have included arrests of opposition figures and protesters, an investigation into opposition leaders for allegedly inciting the military to commit crimes, the passage of a law tightening rules on NGOs and forced resignations of state employees allegedly espousing pro-opposition views.
The supreme tribunal has reviewed material from the electoral authority and agrees that Maduro won the election, court president Caryslia Rodriguez said, adding the decision cannot be appealed.
"The results of the presidential election of July 28 released by the national electoral council, where Nicolas Maduro was elected president of the republic, are validated," Rodriguez said.
The electoral authority has said since the night of the election that Maduro won just over half of votes, although it has not published full tallies.
Venezuelan President Nicolas Maduro is set for another six-year term to begin in January. (AP PHOTO)
The opposition has published online what it says are 83 per cent of voting machine tallies, which give its candidate Edmundo Gonzalez 67 per cent support.
The supreme court has no constitutional right to carry out any electoral functions, making its ruling null, the opposition has said.
"Sovereignty rests with the people and is intransferable. Organs of state emanate from and are subject to popular sovereignty," Gonzalez said in a social media post after the ruling.
A copy of the court's decision will be shared with the attorney general, Rodriguez said, so it can be included in criminal investigations being carried out into supposed irregularities connected to publication of "presumably false" election results online.
Both Gonzalez and opposition leader Maria Corina Machado are being investigated for several crimes, including allegedly inciting members of the military to commit crimes, after they called on security forces to uphold election results.
The United States and some of its allies have urged full publication of the results while Russia, China and others have congratulated Maduro on his victory.
Sources have told Reuters the US has drafted a list of about 60 government officials and family members who could face sanctions in the first punitive measures since the vote but most solutions for the crisis floated by the international community have either been ignored or rejected by the government, the opposition or both.
The ratification gives Maduro, who took office in 2013, another six-year term, set to begin in January.
The president, a long-time ruling party official before he rose to the presidency, had asked the court to verify the results.
The court's judges summoned all the candidates to hand over the copies of voting machine tallies they are entitled to by law.
Gonzalez did not attend the summons.
The opposition says the court, although constitutionally independent, operates as an arm of the ruling party.
The opposition's failure to hand over its copies and Gonzalez's non-appearance are "blatant disrespect," Rodriguez said, and exposes him to sanctions although she did not specify what kind.
The electoral council should publish its definitive results, Rodriguez added, without giving further details.
At least 23 protesters have been killed at anti-government demonstrations since the election and 2400 arrested, according to the United Nations.
Maduro says the demonstrators are extremists and fascists.
