The remaining members of Monty Python will perform at London's O2 Arena - more than 30 years after their last stage performance.
The veteran comedy troupe - John Cleese, Michael Palin, Eric Idle, Terry Gilliam and Terry Jones - announced the news at a madcap launch at London's Playhouse Theatre, where Python musical Spamalot is being performed.
Actor Warwick Davis, who recently appeared in Spamalot, hosted the event for the set who are seen as kings of comedy with their groundbreaking, anarchic comedy series and films.
They promised the return of some of their most famous routines, including a likely performance of the dead parrot sketch, but Cleese has ruled out a re-run of one of his best loved moments, the Ministry of Silly Walks.
"I have an artificial knee and an artificial hip so there's no chance of that," he said.
Idle said: "I think you can expect a little comedy, a lot of pathos, some music and a tiny bit of ancient sex."
The show on July 1 is described as having "modern, typical, Pythonesque twists". Their last major live show was at the Hollywood Bowl in 1982.
"We'll be doing material we've never done live. There'll be quite a lot of that," said Idle, before pointing out most people find new songs to be the low point of most concerts.
"We're hoping people will have forgotten so they'll appear new."
In typical humorous style, the quintet lined up behind the wrong name cards and they answered questions addressed to other members of the team.
Fittingly, the first question came from a Spanish journalist, with Palin responding: "We didn't expect the Spanish inquisition."
Asked why the reunion was being held now, Idle joked: "We're all trying to pay for Terry Jones's mortgage."
Cleese said "at first" the gig would be "a one and only" but did not rule out further performances.
He said Palin - who has gone on to become a celebrated globe-trotting TV adventurer - had "chickened out" of earlier plans to reunite and needed to be convinced about the plan.
Monty Python's Flying Circus was made for TV between 1969 and 1974 and generations of fans can recite lines and whole sketches. The team went on to make films including Monty Python And The Holy Grail (1975) and Monty Python's Life of Brian (1979).
Sixth Python Graham Chapman died of cancer in 1989 aged just 48, and nine years later the five remaining members shared a stage at the Aspen Comedy Festival in the US.
They said they would miss performing with Chapman but he would have a presence on-screen during the show.
Idle said: "We've told him we're going on and if there is a God, he'll be turning up."
The event will be filmed and "we will try and flog it later", he added.
Monty Python Press Conference – The Best Quips
"They had so many bids they had to enlist the help of Sepp Blatter" - Host Warwick Davis explaining how the Pythons chose the location for the gig.
"The winner is Meryl Streep" - Davis again, when announcing the chosen city.
"Nobody expected the Spanish inquisition" - Michael Palin when the first question in the press conference came from a Spanish journalist.
"I think the answer is we are all trying to pay for Terry Jones's mortgage" - Eric Idle's reason for the reunion.
"A little comedy, some pathos, some music and a tiny bit of ancient sex" - John Cleese on what will be in the show.
"I think we should certainly think about touring the world, because I've done it for years" - TV globetrotter Palin on plans for a possible world tour.
"We actually have told him we'll be on and if there is a God, he'll show up" - Eric Idle on the sixth Python Graham Chapman, who died of cancer in 1989 aged just 48.
"I think the clever thing was we waited until the demand had died down" - Idle on returning to the stage more than three decades after their last show.
"That's impossible now because I have an artificial knee and an artificial hip" - Cleese explaining why he will not be doing the Ministry of Silly Walks sketch.