The Cape Town water crisis in South Africa was a period of severe water shortage in the Western Cape region, most notably affecting the City of Cape Town. While dam water levels had been declining since 2015, the Cape Town water crisis peaked during mid-2017 to mid-2018 when water levels hovered between 15 and 30 percent of total dam capacity. In late 2017, there were first mentions of plans for "Day Zero", a shorthand reference for the day when the water level of the major dams supplying the City fell below 13.5 percent. "Day Zero" would herald the start of Level 7 water restrictions, when municipal water supplies would largely be switched off and residents would have to queue for their daily ration of water, making the City of Cape Town the first major city in the world to potentially run out of water. The water crisis occurred at the same time as the still ongoing Eastern Cape drought located in a separate region nearby.
The City of Cape Town implemented significant water restrictions in a bid to curb water usage, and succeeded in reducing its daily water usage by more than half to around 500 million litres (130,000,000 US gal) per day in March 2018. The fall in water usage led the City to postpone its estimate for "Day Zero", and strong rains starting in June 2018 led to dam levels recovering. In September 2018, with dam levels close to 70 percent, the city began easing water restrictions, indicating that the worst of the water crisis was over. Good rains in 2020 effectively broke the drought and resulting water shortage when dam levels reached 95 percent.