Matthew Perry recently hinted there was "big news coming", but now he and Jennifer Aniston, Courteney Cox, Lisa Kudrow, Matt LeBlanc and David Schwimmer have all announced their involvement on social media.
Each of the stars of the hit '90s sitcom, about a group of friends living in New York City trying to navigate life as young adults, have posted the same message on their Instagram, saying: "It's happening..."
Streaming service HBO Max has said they will return for an unscripted special.
The last episode was broadcast in 2004 and ended with a shot of the cast all leaving keys to Monica and Chandler's apartment on the kitchen counter before heading out for a goodbye coffee.
Kevin Reilly, chief content officer of HBO Max, said: "Guess you could call this the one where they all got back together."
He also added that the special will be programmed alongside the entire Friends Library.
"I became aware of Friends when it was in the very early stages of development and then had the opportunity to work on the series many years later and have delighted in seeing it catch on with viewers generation after generation."
He continued: "It taps into an era when friends - and audiences - gathered together in real time, and we think this reunion special will capture that spirit, uniting original and new fans."
Britain's Ben Winston announced on Twitter that he "could not BE anymore excited" to be directing and producing the special, with the emphasis on "be" in a nod to Perry's character Chandler's popular phrase.
All six stars of the show will also be executive producers of the special.