The city has suffered periodic water cuts for years as the crumbling economy has caused widespread power shortages that often leave pumps idle.
But the city-wide cut appeared aimed at stopping the flow of untreated water around Harare, which is at the epicentre of the cholera epidemic that has claimed 425 lives since late August - most in just the last month.
The complete shutdown of water services caught many families by surprise, sending people into the streets carrying containers to search for water from wells or cisterns and adding to the hardships of daily life under President Robert Mugabe's regime.
Some residents have resorted to digging shallow wells in their yards in the hope of finding water, while making another hole to serve as a latrine - which could worsen the sanitary conditions that caused the cholera epidemic.
The Zimbabwe National Water Authority (Zinwa) stopped pumping because it had failed to obtain chemicals to treat the water supply, the government mouthpiece Herald newspaper said.
"Most parts of Harare - including the city centre - did not get water yesterday amid claims by Zinwa staff that the authority had stopped pumping after it ran out of one of the essential chemicals," the Herald reported.
Health Minister David Parirenyatwa, who said Sunday that the cholera caseload had topped 11,000, urged the public to stop shaking hands to prevent the disease from spreading.
Shaking hands is an important part of greeting in Zimbabwe, and the gesture can last for several minutes when close acquaintances meet.
"Although it's part of our tradition to shake hands, it's high time people stopped," Parirenyatwa said in the Herald.
The opposition Movement for Democratic Change again urged Mugabe's government accept large-scale humanitarian relief to cope with the epidemic.
"My appeal to the international community as a matter of urgency is for food and medicine as the country is failing to cope with the humanitarian crisis that has hit Zimbabwe," the party's deputy leader Thokozani Khupe said.
Residents in Harares populous sister city of Chitungwiza told AFP that their taps had also run dry, while some government offices closed due to the lack of water and sanitation in the buildings.
Wealthier residents as well as some churches and businesses have long ago installed deep wells or cisterns.
Long lines formed around the city anywhere that had water flowing, while vendors at the main Mbare market were doing a brisk business in jerrycans.
"Today is one of my busiest days. I have sold more than 20 containers since morning," said George Munetsi, an Mbare vendor who charged 35 US dollars for a 70-litre container - a fortune in a country where 80 percent of the population lives in poverty.
Cholera spreads through the water, when human excrement mixes with drinking water or food.
The disease is a highly contagious, but treatable illness that causes severe diarrhoea and vomiting that can kill a patient.
Although cholera is curable, Zimbabwe hospitals lack drugs, equipment and staff to care for patients.
The disease has already spread into neighbouring South Africa and Botswana, raising fears of a regional crisis. Seven people have died of cholera in South Africa after leaving Zimbabwe.
The cholera epidemic has compounded the daily misery faced by ordinary Zimbabweans, who struggle to survive with the world's highest inflation, last estimated at 231 million percent, while nearly half the population needs emergency food aid.