The US singer is following in the footsteps of Kylie Minogue, Neil Diamond, Dolly Parton, Paul Simon and Barry Gibb.
Diana Ross, 77, will perform on the Sunday of the 2022 edition of the event.
She joins previously announced headliner Billie Eilish on the bill for next year's festival.
Ross said: "I’m so excited and grateful to finally know, that I’ll be seeing you at Glastonbury while on my UK Thank U Tour celebrating my new album of songs, Sunday, June 26, 2022."
Glastonbury tweeted: "We are thrilled to announce that @DianaRoss will play the Sunday legends slot on the Pyramid Stage at #Glastonbury2022."
Festival organiser Emily Eavis added: "I’m thrilled to be able to let you know that the magnificent @DianaRoss is coming to play at @glastonbury next summer.
"We were so excited to book such a legend for Glastonbury 2020 and are so happy that she’s the first to re-confirm for next year."
Last week, Ross released her new album Thank You.
This year, the festival hosted a five-hour livestream event featuring acts including Coldplay, Damon Albarn, Haim, Idles, Jorja Smith, Kano, Michael Kiwanuka, Wolf Alice and DJ Honey Dijon.
Last year, the festival was due to celebrate its 50th anniversary – but it was cancelled due to the coronavirus pandemic.
The 2020 line-up had been due to feature names like US star Kendrick Lamar, Taylor Swift and Sir Paul McCartney, with Ross due to play the legends slot.
Glastonbury will take place from June 22.
Source: Press Association