This is the first election for the former British colony since long-time ruler Robert Mugabe was ousted in a military coup last year.
The main contenders to take the presidency are incumbent president Emmerson Mnangagwa, of Mr Mugabe’s Zanu-PF party, and opposition leader Nelson Chamisa of the Movement for Democratic Change (MDC) Alliance.
Final results are not expected until much later in the week, possibly as late as the weekend, but counting went on all throughout the night.
Who is winning?
Mr Chamisa this morning said he was “winning resoundingly” from results across some 10,000 polling stations.
On Twitter, he wrote: “We’ve done exceedingly well.
“Awaiting ZEC (Zimbabwean Electoral Commission) to perform their constitutional duty to officially announce the people’s election results and we are ready to form the next gvt.”
Mr Chamisa’s claim has yet to be supported by the electoral commission or election officials.
Zimbabwe election results 2018: This is the first election since Robert Mugabe was ousted
This is a historic, watershed moment for Zimbabwe.
After 37 years under repressive rule, with a leader riddled with allegations of corruption and war crimes, young Zimbabweans are excited for an opportunity to exercise their democratic rights.
Whoever wins this election will have a mighty task on his hands: To resuscitate the entirely failed economy and turn the country’s international pariah status around will be no easy feat.
And the two opponents couldn’t be more different.
Zimbabwe election results 2018: Millions of Zimbabweans queued for hours to cast their vote
Mr Mnangagwa, 75, was a long-serving Mugabe aide and has been nicknamed ’The Crocodile’ for his political cunning.
He took over as president after Mr Mugabe was forced to resign after the military coup.
Since then, he has survived a number of assassination attempts, which he blames on supporters of Mr Mugabe.
He has pledged to boost the economy, woo foreign investors and create jobs, and offers the country continuity by remaining under Zanu-PF rule.
Zimbabwe election results 2018: Counting went on all throughout the night.
However, Mr Mnangagwa is associated with some of the worst atrocities committed under his former boss, including heavy involvement in he country’s 1980s civil conflict which saw thousands of people massacred.
Mr Chamisa, 40, is a lawyer and pastor with minimal political experience.
His only experience of power was a stint as a minister in a coalition government a few years ago.
What he has to offer is something most young Zimbabweans seem to be calling for: a radical change.
And of the 5.5 million who registered to vote, about half of those were under 35.
Zimbabwe election results 2018: Mr Chamisa’s tweet this morning
However, Mr Chamisa has been criticised for making unrealistic promises, such as the introduction of a high-speed bullet train and bringing the Olympics to Zimbabwe.
In a surprise press conference on Sunday, the now 94-year-old Robert Mugabe indicated he was backing Mr Chamisa.
He said: “I cannot vote for those who tormented me.
”I hope the choice of voting tomorrow will thrust away the military government and bring us back to constitutionality.”
Mr Mnangagwa has responded to Mr Mugabe’s support of the opposition, saying: “It is clear to all that Chamisa has forged a deal with Mugabe, we can no longer believe that his intentions are to transform Zimbabwe and rebuild our nation.”