Glastonbury's famous Pyramid Stage will remain dark in June, as the festival becomes the latest event to be cancelled due to coronavirus.
Taylor Swift, Sir Paul McCartney and Kendrick Lamar were due to appear, alongside Diana Ross and Dua Lipa.
"We're so sorry that this decision has been made," a statement said. "It was not through choice."
Just six days ago, organiser Emily Eavis said she had "fingers firmly crossed" the event would go ahead.
But after the government advised people to avoid mass gatherings on Monday, cancellation became increasingly likely.
Organisers took the decision before 1 April, when festival-goers were expected to pay the remaining balance of their £270 tickets.
We are so sorry to announce this, but we are going to have to cancel Glastonbury 2020. Tickets for this year will roll over to next year. Full statement below and on our website. Michael & Emily pic.twitter.com/ox8kcQ0HoB— Glastonbury Festival (@glastonbury) March 18, 2020
Fans who had already paid the £50 deposit will be allowed to roll over that sum to next year, guaranteeing "the opportunity to buy a ticket for Glastonbury 2021", organisers said. Refunds will also be available for those who want them.
More than 200,000 people, including 135,000 ticket-holders, would have descended on Worthy Farm in Somerset if the festival had gone ahead from 24 to 28 June.
Other acts on the line-up included Noel Gallagher, Lana Del Rey, Herbie Hancock, the Pet Shop Boys, AJ Tracey and Haim.
"We very much hope that the situation in the UK will have improved enormously by the end of June," said Michael and Emily Eavis in a statement.
"But even if it has, we are no longer able to spend the next three months with thousands of crew here on the farm, helping us with the enormous job of building the infrastructure and attractions."
Saying 2020 would now be an "enforced fallow year" for the festival, they apologised for letting fans down.
"We were so looking forward to welcoming you all for our 50th anniversary with a line-up full of fantastic artists and performers that we were incredibly proud to have booked."
They added: "We look forward to welcoming you back to these fields next year and until then, we send our love and support to all of you."
BBC Radio 2 DJ Jo Whiley echoed many fans' sentiments when she wrote on Twitter: "This is so devastatingly disappointing for so many people on so many levels.
"Next year Glastonbury is going to be off the scale," she added. "But for now much love to Emily Eavis and the Glasto family."
Musician Billy Bragg, who is an annual fixture at the festival, also expressed his disappointment.
Glastonbury AND EastEnders cancelled on the same day! Time to look elsewhere for some cultural input. Taking a dive into this classic again. pic.twitter.com/8cAqVpGbqa— Billy Bragg (@billybragg) March 18, 2020
2/3. We were so looking forward to returning to Worthy Farm and are still processing this news - this festival is incredibly special to us and our hearts go out to @emilyeavis, Michael, and the entire @glastonbury team.— Skunk Anansie (@SkunkAnansie) March 18, 2020
Meanwhile, pop culture journalist Natalie Jamieson issued an open call for the BBC to raid its archive of Glastonbury footage to broadcast an "ultimate Glastonbury line-up" on the last weekend of June.
"Am still gonna need a live-music fix & it could bring *such* joy," she wrote.
Lorna Clarke, the BBC's controller of pop music, later said the broadcaster would "look at providing our audiences with a celebration of Glastonbury in June".
Glastonbury's cancellation comes after BBC Radio 1 cancelled plans to host its Big Weekend festival in Dundee in May.
The announcement also calls into doubt the viability of other UK festivals, including BST Hyde Park, All Points East, Lovebox and Latitude.
In the US, the Coachella and South By Southwest festivals have already been postponed or called off, while concert giants Live Nation and AEG have halted all forthcoming concert tours, with acts like Celine Dion, The Who and Billie Eilish among the artists postponing dates.
Live Nation's share price finished trading at $33.92 (£28.26) on Tuesday - less than half of its value at this time last month.
But many artists - including Coldplay, Christine and the Queens and Yungblud - have started to live-stream concerts to keep fans' spirits up during self-isolation.
Bruce Springsteen also uploaded a full 2009 concert with the E Street Band to YouTube, telling fans to "practice social distancing and stream" live music "from the comfort of your own home".