It will be the first time the band have performed together since 2000
Blur are reforming to play a huge live show in London's Hyde Park next summer - nine years after their last concert as a four-piece band.
Damon Albarn, Graham Coxon, Alex James and Dave Rowntree will reunite for the concert on 3 July.
It will be the first time the band have played in public since performing at London's Royal Festival Hall in 2000, before Coxon left the group in 2002.
Tickets for the gig, which will cost £45, go on sale at 0900 GMT on Friday.
"It just felt it was right again," Albarn told music weekly NME.
"It somehow feels like there's something for us to do again, we're not completely useless or pointless, we've got a reason to exist."
Coxon told the magazine the band were "making public what's been going on a little bit privately".
The announcement has fuelled speculation that the band will also play at next year's Glastonbury Festival, which falls a week before the Hyde Park gig.
But a Glastonbury spokesman said fans should not buy tickets based on unconfirmed reports.
"We are talking to headliners at the moment," he told BBC News.
"There is lots of speculation about who might or might not be playing next year. We're confident it will be as good as Jay-Z. No headliners have been confirmed."
Last month, Albarn told BBC Radio 1's Newsbeat it was "very possible" he would go back to Blur.
The singer confirmed the band members had been meeting up and bassist James had also hinted at a reunion.
Formed in 1989, Blur have recorded seven studio albums and had a string of UK top 10 singles, including number one hits with Country House and Beetlebum.
Their last album, Think Tank, was released in 2003.
Since then, Albarn, 40, has been best known for his Gorillaz pop project with cartoonist Jamie Hewlett.
More recently, the pair have collaborated on Monkey: Journey to the West, a Chinese opera that is running at London's O2 until January and will then tour the world.
Guitarist Coxon, 39, developed his solo career while James, 40, became a writer and now makes cheese on a farm in Oxfordshire.
Drummer Dave Rowntree, 44, was recently selected by the Labour Party to be its candidate for the Cities of London and Westminster at the next general election.