The Madrid Open has been cancelled after organisers were advised by the Spanish health ministry not to hold it amid the city's "deteriorating" coronavirus situation.
The clay-court event was set to start in the Spanish capital on 12 September.
"We have no choice but to cancel the tournament due to the complex situation that Covid-19 continues to generate in every regard," said organisers.
Spanish great Rafael Nadal was among the players who signed up to play.
Spain has recorded more than 302,000 cases of coronavirus since the start of the pandemic, and 28,498 deaths, according to the latest figures released on Tuesday.
Data from the European Centre for Disease Prevention and Control (ECDC) show the rate of infection in Spain is rising rapidly again, particularly in the Madrid and Aragon regions.
"After a spike in Covid-19 cases, the community of Madrid announced few days ago a number of new measures to control the virus' spread," said a Madrid Open statement.
"These including a directive that social gatherings are to be reduced to 10 people, both in public and private meetings, further reducing the feasibility of operating the tournament."
The ATP and WTA event is a key tournament in the European clay-court season, which culminates with the French Open.
Both the Madrid Open an the French Open was originally scheduled for May before being pushed back to September.
The French Open is scheduled to start on 27 September, with organisers hoping to allow up to 60% of crowd capacity at Roland Garros.
Professional tennis resumed with the WTA event in Palermo this week, while the ATP Tour returns later this month with the Western and Southern Open.
That event, usually held in Cincinnati, is being staged in a safety bubble in New York from 22 August, immediately before the US Open takes place at Flushing Meadows on 31 August.