The ‘Hello’ singer revealed she will be belting out her hits on the Pyramid Stage during one of her gigs at London’s O2 Arena.
"Who's going to Glastonbury this year?" she asked the audience. "See you there. I'll be there. I'll be headlining on the Saturday night this year."
"I've had to keep that secret for years!" the star added.
Glastonbury later confirmed the news on Twitter.
“As @Adele just announced live on stage in London, she will headline Saturday night at this year's Glastonbury Festival!” they tweeted.
Adele will join Coldplay and Muse at the top of the bill when the festival takes place in June.
Festival organiser Emily Eavis also took to twitter to share her excitement at the news, tweeting: "What a great honour it is to have the wonderful Adele confirmed for this year's Saturday night headline spot on the Pyramid Stage!"
Earlier this week, Adele teased fans in Manchester that she would "see them at Glastonbury", but not necessarily as a performer.
"I'll be dressed as Elsa and my kid will be Olaf," she said, referring to characters from the Disney film 'Frozen'.
Adele's latest album, ‘25’, has sold more than 19 million copies worldwide in just four months.
Adele previously admitted she didn’t know if she could play to such a large crowd as Glastonbury after she became "frozen with fear" when she saw Kanye West perform in 2015.
"I wasn't anywhere near the stage and it was the biggest crowd I'd ever seen," she said. "I just thought: 'I don't know if I can do that.'"
This year's Glastonbury festival takes place in Somerset from 22 to 26 June.