Speaking to her thousands of fans at the O2, Adele asked in her trademark casual manner: "Who's going to Glastonbury this year? See you there. I'll be there. I'll be headlining on the Saturday night this year."
The 27-year-old added: "I've had to keep that secret for years!"
"Who's going to Glastonbury this year? See you there. I'll be there," said Adele
While Adele hasn't reiterated her message on Twitter, the news was confirmed on the official Glastonbury Festival account. "As @Adele just announced live on stage in London, she will headline Saturday night at this year's Glastonbury Festival!" the post read.
Emily Eavis, the co-organiser of Glastonbury and daughter of its founder Michael Eavis, also tweeted that it was a "great honour" to have Adele headline Saturday night on the Pyramid Stage.
Adele now joins Muse and Coldplay at the top of the bill. The British band, fronted by Chris Martin, are set to make history as they will become the first act to headline Glastonbury for a record fourth time.
ELO have also been confirmed to play the teatime slot on Sunday afternoon. Other acts will be revealed at a later date.
While fans were previously speculating that the Foo Fighters may headline, many will no doubt be thrilled to hear that Adele is taking the top spot. Some will also be wondering if the Rolling in the Deep chart-topper will pull out a few surprises.
The Hello singer added: "I've had to keep that secret for years!"
Earlier this week Adele invited a couple on stage after she spotted them getting engaged in the audience. HELLO! Online witnessed the sweet moment the lovebirds, who have now been identified as Natalie King and Johnny Biggle, joined the singer on stage to share their story.
The pair have been going out for 12 and a half years and Johnny decided to propose during Make You Feel My Love, which they call "our song".
"Did you just get engaged? Oh my god! I thought there was a fight at first!" said Adele. "I saw all of the camera phone lights at first and then I saw arms went up and I saw sweet kissing."