The French Open has been moved to September and October as a result of the coronavirus pandemic, BBC reports.
The event at Roland Garros was due to be played from 24 May to 7 June, but instead will take place between 20 September and 4 October.
That means it will begin just one week after the completion of the US Open in New York.
All professional tennis across the world is currently suspended until at least 20 April.
The French Open is usually the second Grand Slam tournament of the year, after the Australian Open, and the finale of the clay court part of the season.
It will now be the final major of the year, and the new dates clash with a number of other events, including the Laver Cup, an annual men's event between a team from Europe and a team representing the rest of the world.
The French tennis federation said the move was made to "guarantee the health and safety of all those involved in the preparation of the tournament".
It added: "While no one today can predict what the health situation will be like on 18 May [when qualification was due to start], the lockdown measures in force make it impossible to prepare for it and therefore to organise it on the dates initially planned."
The announcement that Roland Garros will not take place in May came as no surprise whatsoever.
But the French Federation's unilateral decision to move the date until late September has caused jaws to drop throughout the sport.
Not only would it clash with the Laver Cup, but also with the start of the traditional Asian swing on both the ATP and the WTA Tour.
It is a bold move; or an audacious land grab As Britain's Jamie Murray said on social media: "The frustration will be that the FFT acted on its own with no regard for any of the other stakeholders in tennis".
There is already some rancour between the players and the Grand Slams. Many professionals feel they are not getting a large enough share of the profits the Slams generate.
When the two tours deliver their response later this week, it will make for interesting reading.
The United States Tennis Association (USTA) says it has not ruled out the possibility of switching the US Open to a later date, after the French Open was moved back to September.
USTA says it is assessing all options but is not currently implementing any changes to its schedule.
The US Open, which is played in New York, is due to begin on 31 August.
USTA also criticised the French Tennis Federation's unilateral decision to move the dates of Roland Garros.
The event in Paris was due to be played from 24 May to 7 June, but instead will take place from 20 September to 4 October.
That means it will begin just one week after the completion of the US Open.
"At a time when the world is coming together, we recognise that such a decision should not be made unilaterally," the statement said.
"Therefore the USTA would only [act] in full consultation with the other Grand Slam tournaments, the WTA and ATP, the ITF and our partners, including the Laver Cup."
